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Calendar-Aware Date/Time UDT Sample

Storing dates as strings can be confusing because dates are meaningless without understanding what calendar system is being used.The CADatetime sample defines two user-defined data types, CADatetime and CADate, which provide calendar-aware handling of dates and times.

To create and run this project the following the following software must be installed:

  • SQL Server or SQL Server Express. You can obtain SQL Server Express free of charge from the SQL Server Express Documentation and Samples Web site

  • The AdventureWorks database that is available at the SQL Server Developer Web site

  • .NET Framework SDK 2.0 or later or Microsoft Visual Studio 2005 or later. You can obtain .NET Framework SDK free of charge.

  • In addition, the following conditions must be met:

  • The SQL Server instance you are using must have CLR integration enabled.

  • In order to enable CLR integration, perform the following steps:

    Enabling CLR Integration

    • Execute the following Transact-SQL commands:

    sp_configure 'clr enabled', 1

    GO

    RECONFIGURE

    GO

    Note Note

    To enable CLR, you must have ALTER SETTINGS server level permission, which is implicitly held by members of the sysadmin and serveradmin fixed server roles.

  • The AdventureWorks database must be installed on the SQL Server instance you are using.

  • If you are not an administrator for the SQL Server instance you are using, you must have an administrator grant you CreateAssembly permission to complete the installation.

Create and run the sample by using the following instructions:

  1. Open a Visual Studio or .NET Framework command prompt.

  2. If necessary, create a directory for your sample. For this example, we will use C:\MySample.

  3. In c:\MySample, create CalendarAware.cs and copy the C# sample code (below) into the file.

  4. In c:\MySample, create the file calendars.txt and copy the sample code into the file.

  5. In c:\MySample, create the file calendars.ar-SA.txt and copy the following into the file:

    • ; the default calendar for this culture

    • DefaultCalendarID = 1

  6. In c:\MySample, create the file calendars.ja.txt and copy the following into the file:

    • ; the default calendar for this culture

    • DefaultCalendarID = 3

  7. In c:\MySample, create the file calendars. zh-CN.txt and copy the following into the file:

    • ; the default calendar for this culture

    • DefaultCalendarID = 8

  8. In c:\MySample, create the file build.com and copy the following into the file:

    • resgen calendars.txt

    • resgen calendars.ar-SA.txt

    • resgen calendars.ja.txt

    • resgen calendars.zh-CN.txt

    • al /t:lib /culture:ar-SA /embed:calendars.ar-SA.resources /out:CADatetime.resources.ar-SA.dll

    • al /t:lib /culture:ja /embed:calendars.ja.resources /out:CADatetime.resources.ja.dll

    • al /t:lib /culture:zh-CN /embed:calendars.zh-CN.resources /out:CADatetime.resources.zh-CN.dll

    • al /t:lib /culture:"" /embed:calendars.resources /out:CADatetime.resources.dll

  9. Build the satellite assembles by executing the file build at the command prompt.

  10. Compile the sample code from the command line prompt by executing the following:

    • Csc /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.Data.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.dll /reference:C:\Windows\Microsoft.NET\Framework\v2.0.50727\System.XML.dll /out:CADateTime.dll /target:library CalendarAwareDate.cs

  11. Copy the Transact-SQL installation code into a file and save it as Install.sql in the sample directory.

  12. If the sample is installed in a directory other then C:\MySample\, edit the file Install.sql as indicated to point to that location.

  13. Deploy the assembly and stored procedure by executing

    • sqlcmd -E -I -i install.sql

  14. Copy Transact-SQL test command script into a file and save it as test.sql in the sample directory.

  15. Execute the test script with the following command

    • sqlcmd -E -I -i test.sql

  16. Copy the Transact-SQL cleanup script into a file and save it as cleanup.sql in the sample directory.

  17. Execute the script with the following command

    • sqlcmd -E -I -i cleanup.sql

The following are the code listings for this sample.

C#

    using System;
    using System.Data.Sql;
    using System.Data.SqlTypes;
    using System.Globalization;
    using System.Resources;
    using System.Text;
    using System.Reflection;
    using System.Collections.Generic;
    using System.Xml;
    using System.Xml.Serialization;
    using System.Xml.Schema;
    using System.IO;

[assembly: System.Resources.NeutralResourcesLanguage("", System.Resources.UltimateResourceFallbackLocation.Satellite)]


    /// <summary>
    /// A date value in the specified calendar system.
    /// </summary>
    [Serializable]
    [Microsoft.SqlServer.Server.SqlUserDefinedType(Microsoft.SqlServer.Server.Format.Native, IsByteOrdered = true)]
    public struct CADate : INullable, IXmlSerializable
    {
        // This type uses days == 0 as the way to designate a NULL value

        const string CADateSchema =
            "<xs:schema targetNamespace=\"http://schemas.microsoft.com/sqlserver/2004/08/CADate\" " +
                "xmlns=\"http://schemas.microsoft.com/sqlserver/2004/07/CADate\" " +
                "elementFormDefault=\"qualified\"" +
                "xmlns:xs=\"http://www.w3.org/2001/XMLSchema\" >" +
                "<xs:element name=\"CADate\" >" +
                    "<xs:complexType mixed=\"true\" >" +
                        "<xs:attribute name=\"IsNull\" use=\"required\" type=\"xs:boolean\" />" +
                        "<xs:attribute name=\"Year\" type=\"xs:int\"/>" +
                        "<xs:attribute name=\"Month\" type=\"xs:int\"/>" +
                        "<xs:attribute name=\"Day\" type=\"xs:int\"/>" +
                        "<xs:attribute name=\"Calendar\" type=\"xs:string\"/>" +
                    "</xs:complexType>" +
                "</xs:element>" +
            "</xs:schema>";

        private const uint NullDay = 0;

        private static readonly char[] dateChars = new char[] { 'd', 'M', 'y' };
        private static readonly char[] allowedSinglePatternChars = new char[] { 'd', 'D', 'm', 'M', 'y', 'Y', '/', '%' };
        private static readonly char[] allowedDoublePatternChars = new char[] { 'g', '\\' };

        /// <summary>
        ///     Each tick is 100 nanoseconds.  This conversion factor when multipled by the number of
        ///     days yields the number of ticks which make up that day.  Ticks are interesting as they
        ///     can be used to construct DateTime instances in order to perform various date based computations.
        /// </summary>
        private const long DaysToTicksConversionFactor = 10L * 1000L * 1000L * 60L * 60L * 24L;

        /// <summary>
        /// The number of days since the calendar started (January 1, 1)
        /// </summary>
        private uint days;

        /// <summary>
        /// Which calendar is used for this date and time
        /// </summary>
        private byte calendarId;

        /// <summary>
        /// construct a CADate from the specified datetime using the default calendar.
        /// </summary>
        /// <param name="dt">DateTime</param>
        public CADate(DateTime dt)
            : this(dt, CalendarInfo.DefaultCalendarId)
        {
        }

        /// <summary>
        /// Construct a calendar aware date for the specified year/month/day using the default calendar
        /// </summary>
        /// <param name="year"></param>
        /// <param name="month"></param>
        /// <param name="day"></param>
        public CADate(int year, int month, int day)
            : this(new DateTime(year, month, day, CalendarInfo.DefaultCalendar))
        {
        }

        /// <summary>
        ///     Converts a DateTime instance and a calendar into a calendar aware date instance.
        /// </summary>
        /// <param name="dt">A specific point in time</param>
        /// <param name="calendarId">A specific calendar system</param>
        private CADate(DateTime dt, int calendarId)
        {
            this.days = (uint)(dt.Ticks / DaysToTicksConversionFactor);
            this.calendarId = (byte)calendarId;
        }

        /// <summary>
        /// the current CADate
        /// </summary>
        /// <value></value>
        public static CADate Now
        {
            get
            {
                return new CADate(DateTime.Now);
            }
        }

        public static string CurrentCalendarName
        {
            get
            {
                return CalendarInfo.DefaultCalendar.GetType().Name;
            }
        }

        /// <summary>
        /// return the null value for this type
        /// </summary>
        /// <value></value>
        public static CADate Null
        {
            get
            {
                CADate caDate = new CADate();
                caDate.days = NullDay;

                return caDate;
            }
        }

        /// <summary>
        /// is this value null
        /// </summary>
        /// <value></value>
        public bool IsNull
        {
            get
            {
                return this.days == NullDay;
            }
        }

        public Calendar Calendar
        {
            get
            {
                return CalendarInfo.Calendars[this.calendarId];
            }
        }

        public string CalendarName
        {
            get
            {
                return this.Calendar.GetType().Name;
            }
        }

        // Accessors for parts of the date 

        public int Year
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetYear(this.DateTime);
            }
        }

        public int Month
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetMonth(this.DateTime);
            }
        }

        public int DayOfMonth
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetDayOfMonth(this.DateTime);
            }
        }

        public int Day
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetDayOfYear(this.DateTime);
            }
        }

    
        public uint Days
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.days;
            }
        }

        /// <summary>
        /// convert to datetime
        /// </summary>
        /// <value></value>
        public DateTime DateTime
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return new DateTime(this.Days * DaysToTicksConversionFactor);
            }
        }

        /// <summary>
        /// parse the given string and return a calendar aware date.
        /// </summary>
        /// <param name="sqlString"></param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = false,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADate Parse(SqlString sqlString)
        {
            if (sqlString.IsNull)
            {
                return CADate.Null;
            }

            return new CADate(DateTime.Parse(sqlString.Value, DateTimeFormatInfo.CurrentInfo));
        }

        /// <summary>
        /// Construct a CADate from the specified format, using the current culture
        /// </summary>
        /// <param name="data">the string to be parsed</param>
        /// <param name="format">the format string</param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = true,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADate ParseUsingFormat(string data, string format)
        {
            if (data == null || format == null)
            {
                return CADate.Null;
            }

            return new CADate(
                DateTime.ParseExact(
                data,
                FilterDateFormat(format),
                DateTimeFormatInfo.CurrentInfo));
        }

        // The following methods are intended to be callable from tsql.  That is why they are static.

        /// <summary>
        /// Create a new CADate from a SqlDateTime
        /// </summary>
        /// <param name="sqlDateTime"></param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = false,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADate FromSqlDateTime(SqlDateTime sqlDateTime)
        {
            if (sqlDateTime.IsNull)
            {
                return CADate.Null;
            }

            return new CADate(sqlDateTime.Value);
        }

        /// <summary>
        /// Creates a CADateTime from a Sql DateTime instance and a specific calendar.
        /// </summary>
        /// <param name="sqlDateTime">When</param>
        /// <param name="calendarName">The short name of the desired calendar</param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = true, IsMutator = false, IsPrecise = false,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADate FromSqlDateTimeAndCalendar(SqlDateTime sqlDateTime, string calendarName)
        {
            return new CADate(sqlDateTime.Value, CalendarInfo.GetCalendarId(calendarName));
        }

        /// <summary>
        /// Create a new CADate from the year/month/day
        /// </summary>
        /// <param name="year"></param>
        /// <param name="month"></param>
        /// <param name="day"></param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = true,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADate FromYearMonthDay(int year, int month, int day)
        {
            return new CADate(year, month, day);
        }

        public static SqlBoolean operator ==(CADate xCADate, CADate yCADate)
        {
            if (xCADate.IsNull || yCADate.IsNull)
            {
                return SqlBoolean.Null;
            }

            return xCADate.DateTime == yCADate.DateTime;
        }

        public static SqlBoolean operator !=(CADate xCADate, CADate yCADate)
        {
            if (xCADate.IsNull || yCADate.IsNull)
            {
                return SqlBoolean.Null;
            }

            return xCADate.DateTime != yCADate.DateTime;
        }

        // Conversions to other representations of the date

        /// <summary>
        /// convert the date to string
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            if (this.IsNull)
            {
                return null;
            }

            return string.Format(
                CultureInfo.CurrentUICulture,
                DayMonthYearFormatString(),
                this.DayOfMonth,
                this.Month,
                this.Year);
        }

        /// <summary>
        /// Return a string representation of this date, in the Gregorian calendarId
        /// </summary>
        /// <returns></returns>
        public string ToGregorianString()
        {
            if (this.IsNull)
            {
                return null;
            }

            return this.DateTime.ToString("d", DateTimeFormatInfo.CurrentInfo);
        }

        /// <summary>
        /// Convert the date to string, using the specified format
        /// </summary>
        /// <param name="format">Format string</param>
        /// <returns></returns>
        public string ToGregorianStringUsingFormat(string format)
        {
            if (this.IsNull)
            {
                return null;
            }

            return this.DateTime.ToString(
                FilterDateFormat(format),
                DateTimeFormatInfo.CurrentInfo);
        }

        /// <summary>
        /// Convert to sql datetime
        /// </summary>
        /// <returns></returns>
        public SqlDateTime ToSqlDateTime()
        {
            return new SqlDateTime(this.DateTime);
        }

        // Manipulation of date parts

        public CADate AddYears(int years)
        {
            return new CADate(this.Calendar.AddYears(this.DateTime, years));
        }

        public CADate AddDays(int daysToAdd)
        {
            return new CADate(this.Calendar.AddDays(this.DateTime, daysToAdd));
        }

        public CADate AddMonths(int months)
        {
            return new CADate(this.Calendar.AddMonths(this.DateTime, months));
        }

        public double DiffDays(CADate other)
        {
            return this.DateTime.Subtract(other.DateTime).TotalDays;
        }

        // Hashing and comparison methods

        public override int GetHashCode()
        {
            return this.DateTime.GetHashCode();
        }

        public override bool Equals(object obj)
        {
            if (!(obj is DateTime))
            {
                return false;
            }

            DateTime dt = (DateTime)obj;
            return this.DateTime.Equals(dt);
        }

        public XmlSchema GetSchema()
        {
            StringReader sr = new StringReader(CADateSchema);
            XmlSchema schema = XmlSchema.Read(
                sr,
                new ValidationEventHandler(this.ValidationHandler));
            sr.Dispose();

            return schema;
        }

        public void ReadXml(XmlReader reader)
        {
            if (reader == null)
            {
                throw new ArgumentNullException("reader");
            }

            reader.MoveToContent();
            if (reader.GetAttribute("IsNull").Equals("true"))
            {
                this.days = NullDay;
            }
            else
            {
                string calendarName = reader.GetAttribute("Calendar");
                Calendar requestedCalendar 
                    = CalendarInfo.Calendars[CalendarInfo.GetCalendarId(calendarName)];

                this.days = (uint)(new DateTime(
                    int.Parse(
                        reader.GetAttribute("Year"),
                        CultureInfo.CurrentUICulture),
                    int.Parse(
                        reader.GetAttribute("Month"), 
                        CultureInfo.CurrentUICulture),
                    int.Parse(
                        reader.GetAttribute("Day"), 
                        CultureInfo.CurrentUICulture),
                        requestedCalendar).Ticks / DaysToTicksConversionFactor);
            }
        }

        public void WriteXml(XmlWriter writer)
        {
            if (writer == null)
            {
                throw new ArgumentNullException("writer");
            }

            writer.WriteStartElement(
                "CADate",
                "http://schemas.microsoft.com/sqlserver/2004/08/CADate");
            writer.WriteAttributeString("IsNull", this.IsNull.ToString(CultureInfo.CurrentUICulture));
            if (!this.IsNull)
            {
                writer.WriteAttributeString("Year", this.Year.ToString(CultureInfo.CurrentUICulture));
                writer.WriteAttributeString("Month", this.Month.ToString(CultureInfo.CurrentUICulture));
                writer.WriteAttributeString("Day", this.Day.ToString(CultureInfo.CurrentUICulture));
                writer.WriteAttributeString("Calendar", this.Calendar.GetType().ToString());
            }

            writer.WriteEndElement();
        }

        // DateTime.ParseExact takes a "format" string which describes how to present the date and time.
        // This method filters out any formatting characters which conflict 
        private static string FilterDateFormat(string format)
        {
            StringBuilder sb = new StringBuilder(format.Length);
            for (int i = 0; i < format.Length; i++)
            {
                char element = format[i];
                bool doubled = (i + 1 < format.Length)
                    && (element.Equals(format[i + 1]) || element.Equals('\\'));
                if (Array.IndexOf<char>(allowedSinglePatternChars, element) > -1 ||
                    char.IsWhiteSpace(element))
                {
                    sb.Append(element);
                }
                else if (doubled && (Array.IndexOf<char>(allowedDoublePatternChars, element) > -1))
                {
                    sb.Append(element);
                    sb.Append(format[++i]);
                }
            }

            return sb.ToString();
        }

        // Returns a string suitable for use with string.Format which displays
        // day, month, and year components in a culture appropriate way.
        private static string DayMonthYearFormatString()
        {
            string cultureDatePattern = CultureInfo.CurrentCulture.DateTimeFormat.ShortDatePattern;
            return CalendarInfo.SubstitutePositionForCharacters(dateChars, cultureDatePattern);
        }

        
        private void ValidationHandler(object sender, ValidationEventArgs args)
        {
            throw new ApplicationException(args.Message);
        }
    }
    public static class CalendarInfo
    {
        public const byte MaxCalendarId = 0xff;
        private readonly static char[] stringFormatChars; // = new char[] { 't' };
        private static readonly Calendar defaultCalendar; // = new GregorianCalendar();
        private static readonly int defaultCalendarId;
        private static readonly Calendar[] calendars;

        /// <summary>
        /// Initialize the calendar array, one for each possible calendar
        /// </summary>
        static CalendarInfo()
        {
            stringFormatChars = new char[] { 't' };

            ResourceManager rm = new ResourceManager("calendars", Assembly.GetExecutingAssembly());

            int numCalendars = int.Parse(rm.GetString("NumCalendars"), CultureInfo.CurrentUICulture);
            if (numCalendars > MaxCalendarId)
            {
                throw new ArgumentOutOfRangeException("Does not support more than 255 calendars");
            }

            calendars = new Calendar[numCalendars];
            for (int i = 0; i < numCalendars; i++)
            {
                string typeName = rm.GetString(i.ToString(CultureInfo.CurrentUICulture));
                calendars[i] = (Calendar)Activator.CreateInstance(Type.GetType(typeName, true));
            }

            defaultCalendarId = int.Parse(rm.GetString("DefaultCalendarID"), CultureInfo.CurrentUICulture);
            defaultCalendar = calendars[defaultCalendarId];
        }

        public static Calendar DefaultCalendar
        {
            get
            {
                return CalendarInfo.defaultCalendar;
            }
        }

        public static int DefaultCalendarId
        {
            get
            {
                return CalendarInfo.defaultCalendarId;
            }
        }

     
        public static Calendar[] Calendars
        {
            get
            {
                return CalendarInfo.calendars;
            }
        }

    
        public static int GetCalendarId(string calendarName)
        {
            for (int i = 0; i < calendars.Length; i++)
            {
                if (calendars[i].GetType().Name == calendarName)
                {
                    return i;
                }
            }

            throw new ArgumentException("Unknown calendar: " + calendarName);
        }

        // Returns a string suitable for use with string.Format which displays
        // either date or datetime components in a culture appropriate way.
        public static string SubstitutePositionForCharacters(Char[] characters, string pattern)
        {
            StringBuilder sb = new StringBuilder();
            char lastChar = ' ';
            for (int i = 0; i < pattern.Length; i++)
            {
                char c = pattern[i];
                int position = Array.IndexOf<char>(characters, c);
                if (position != -1)
                {
                    if (lastChar != c)
                    {
                        sb.Append('{');
                        sb.Append(position);

                        // If this isn't a string format char, it is a numeric format char.
                        // In that case we need to get the correct number of digits from
                        // the pattern.
                        if (Array.IndexOf<char>(stringFormatChars, c) == -1)
                        {
                            // Decimal number with the appropriate minimum number of digits
                            sb.AppendFormat(":d{0:d}", CountRun(c, pattern, i));
                        }

                        sb.Append('}');
                    }
                }
                else
                {
                    sb.Append(c);
                }

                lastChar = c;
            }

            return sb.ToString();
        }

        // Given that you have found character c in a pattern, count how many instances of that
        // character occur at that position before another character or the end of the string is reached.
        
        public static int CountRun(char chr, string pattern, int start)
        {
            if (pattern == null)
            {
                throw new ArgumentNullException("pattern");
            }

            int result = 1;
            for (int i = start + 1; i < pattern.Length; i++)
            {
                if (pattern[i] == chr)
                {
                    result += 1;
                }
                else
                {
                    break;
                }
            }

            return result;
        }
    }
    /// <summary>
    /// A datetime value in the specified calendar system.
    /// </summary>
    [Serializable]
    [Microsoft.SqlServer.Server.SqlUserDefinedType(Microsoft.SqlServer.Server.Format.Native, IsByteOrdered = true, ValidationMethodName = "IsValid")]
    public struct CADateTime : INullable, IXmlSerializable
    {
        const string CADateTimeSchema =
            "<xs:schema targetNamespace=\"http://schemas.microsoft.com/sqlserver/2004/08/CADateTime\" " +
                "xmlns=\"http://schemas.microsoft.com/sqlserver/2004/07/CADate\" " +
                "elementFormDefault=\"qualified\"" +
                "xmlns:xs=\"http://www.w3.org/2001/XMLSchema\" >" +
                "<xs:element name=\"CADate\" >" +
                    "<xs:complexType mixed=\"true\" >" +
                        "<xs:attribute name=\"IsNull\" use=\"required\" type=\"xs:boolean\" />" +
                        "<xs:attribute name=\"Year\" type=\"xs:int\"/>" +
                        "<xs:attribute name=\"Month\" type=\"xs:int\"/>" +
                        "<xs:attribute name=\"Day\" type=\"xs:int\"/>" +
                        "<xs:attribute name=\"Hour\" type=\"xs:int\">" +
                        "<xs:attribute name=\"Minute\" type=\"xs:int\">" +
                        "<xs:attribute name=\"Second\" type=\"xs:int\">" +
                        "<xs:attribute name=\"Calendar\" type=\"xs:string\"/>" +
                    "</xs:complexType>" +
                "</xs:element>" +
            "</xs:schema>";

        static readonly char[] datetimeChars = new char[] { 'd', 'M', 'y', 'h', 'H', 'm', 's', 't' };

        // This type uses ticks == 0 as the way to designate a NULL value
        private const long NullTicks = 0;

        /// <summary>
        /// What date and time this is as ticks from midnight January 1, 1
        /// </summary>
        private long dtTicks;

        /// <summary>
        /// Which calendar is used for this date and time
        /// </summary>
        private byte calendarId;

        /// <summary>
        /// Construct a CADateTime from the specified datetime using the default calendar.
        /// </summary>
        /// <param name="dt">DateTime</param>
        public CADateTime(DateTime dt)
            : this(dt, CalendarInfo.DefaultCalendarId)
        {
        }

        /// <summary>
        /// Construct a calendar aware datetime for the specified year/month/day using the default calendar
        /// </summary>
        /// <param name="year"></param>
        /// <param name="month"></param>
        /// <param name="day"></param>
        public CADateTime(int year, int month, int day)
            : this(new DateTime(year, month, day, CalendarInfo.DefaultCalendar))
        {
        }

        /// <summary>
        ///     Converts a DateTime instance and a calendar into a calendar aware datetime instance.
        /// </summary>
        /// <param name="dt">A specific point in time</param>
        /// <param name="calendarId">A specific calendar system</param>
        private CADateTime(DateTime dt, int calendarId)
        {
            this.dtTicks = dt.Ticks;
            this.calendarId = (byte)calendarId;
        }

        /// <summary>
        /// return the null value for this type
        /// </summary>
        /// <value></value>
        public static CADateTime Null
        {
            get
            {
                CADateTime dt = new CADateTime();
                dt.dtTicks = NullTicks;

                return dt;
            }
        }

        /// <summary>
        /// the current CADateTime
        /// </summary>
        /// <value></value>
        public static CADateTime Now
        {
            get
            {
                return new CADateTime(DateTime.Now);
            }
        }

        public static string CurrentCalendarName
        {
            get
            {
                return CalendarInfo.DefaultCalendar.GetType().Name;
            }
        }

        /// <summary>
        /// is this value null
        /// </summary>
        /// <value></value>
        public bool IsNull
        {
            get
            {
                return this.Ticks == NullTicks;
            }
        }

        public int Year
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetYear(this.DateTime);
            }
        }

        public int Month
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetMonth(this.DateTime);
            }
        }

        public int DayOfMonth
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetDayOfMonth(this.DateTime);
            }
        }

        public int Day
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetDayOfYear(this.DateTime);
            }
        }

        public int Hour
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetHour(this.DateTime);
            }
        }

        public int Minute
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetMinute(this.DateTime);
            }
        }

        public int Second
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetSecond(this.DateTime);
            }
        }

        /// <summary>
        /// Milliseconds
        /// </summary>
        /// <value></value>
        public double Milliseconds
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.Calendar.GetMilliseconds(this.DateTime);
            }
        }

        public long Ticks
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get
            {
                return this.dtTicks;
            }
        }

        /// <summary>
        /// convert to datetime
        /// </summary>
        /// <value></value>
        public DateTime DateTime
        {
            [Microsoft.SqlServer.Server.SqlMethod(IsDeterministic = true, IsPrecise = true)]
            get { return new DateTime(this.dtTicks); }
        }

        public Calendar Calendar
        {
            get
            {
                return CalendarInfo.Calendars[this.calendarId];
            }
        }

        public string CalendarName
        {
            get
            {
                return this.Calendar.GetType().Name;
            }
        }

        /// <summary>
        /// parse the given string and return a calendar aware datetime.
        /// </summary>
        /// <param name="sqlString"></param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = true,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADateTime Parse(SqlString sqlString)
        {
            if (sqlString.IsNull)
            {
                return CADateTime.Null;
            }

            return new CADateTime(
                DateTime.Parse(
                    sqlString.Value,
                    DateTimeFormatInfo.CurrentInfo));
        }

        /// <summary>
        /// Construct a CADateTime from the specified format, using the current culture
        /// </summary>
        /// <param name="data">the string to be parsed</param>
        /// <param name="format">the format string</param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = true,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADateTime ParseUsingFormat(string data, string format)
        {
            if (data == null || format == null)
            {
                return CADateTime.Null;
            }

            return new CADateTime(DateTime.ParseExact(data, format, DateTimeFormatInfo.CurrentInfo));
        }

        /// <summary>
        /// Create a new CADateTime from a SqlDateTime
        /// </summary>
        /// <param name="sqlDateTime"></param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = true,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADateTime FromSqlDateTime(SqlDateTime sqlDateTime)
        {
            if (sqlDateTime.IsNull)
            {
                return CADateTime.Null;
            }

            return new CADateTime(sqlDateTime.Value);
        }

        /// <summary>
        /// Creates a CADateTime from a Sql DateTime instance and a specific calendar.
        /// </summary>
        /// <param name="sqlDateTime">When</param>
        /// <param name="calendarName">The short name of the desired calendar</param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = true, IsMutator = false, IsPrecise = true,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADateTime FromSqlDateTimeAndCalendar(SqlDateTime sqlDateTime, string calendarName)
        {
            return new CADateTime(sqlDateTime.Value, CalendarInfo.GetCalendarId(calendarName));
        }

        /// <summary>
        /// Create a new CADateTime from the year/month/day
        /// </summary>
        /// <param name="year"></param>
        /// <param name="month"></param>
        /// <param name="day"></param>
        /// <returns></returns>
        [Microsoft.SqlServer.Server.SqlMethod(DataAccess = Microsoft.SqlServer.Server.DataAccessKind.None, IsDeterministic = false, IsMutator = false, IsPrecise = true,
        SystemDataAccess = Microsoft.SqlServer.Server.SystemDataAccessKind.None)]
        public static CADateTime FromYearMonthDay(int year, int month, int day)
        {
            return new CADateTime(year, month, day);
        }

        public static SqlBoolean operator ==(CADateTime xCADateTime, CADateTime yCADateTime)
        {
            if (xCADateTime.IsNull || yCADateTime.IsNull)
            {
                return SqlBoolean.Null;
            }

            return xCADateTime.DateTime == yCADateTime.DateTime;
        }

        public static SqlBoolean operator !=(CADateTime xCADateTime, CADateTime yCADateTime)
        {
            if (xCADateTime.IsNull || yCADateTime.IsNull)
            {
                return SqlBoolean.Null;
            }

            return xCADateTime.DateTime != yCADateTime.DateTime;
        }

        /// <summary>
        /// convert the datetime to string
        /// </summary>
        /// <returns></returns>
        public override string ToString()
        {
            if (this.IsNull)
            {
                return null;
            }

            bool afternoon = this.Hour >= 12;
            int twelveHour = this.Hour;
            if (twelveHour == 0)
            {
                twelveHour = 12;
            }
            else if (twelveHour > 12)
            {
                twelveHour = twelveHour - 12;
            }

            return string.Format(
                CultureInfo.CurrentCulture,
                DateTimeFormatString(),
                this.DayOfMonth,
                this.Month,
                this.Year,
                twelveHour,
                this.Hour,
                this.Minute,
                this.Second,
                afternoon
                    ? CultureInfo.CurrentCulture.DateTimeFormat.PMDesignator
                    : CultureInfo.CurrentCulture.DateTimeFormat.AMDesignator);
        }

        /// <summary>
        /// convert the datetime to string, using the specified format
        /// </summary>
        /// <param name="format">Format string</param>
        /// <returns></returns>
        public string ToGregorianStringUsingFormat(string format)
        {
            if (this.IsNull)
            {
                return null;
            }

            return this.DateTime.ToString(format, DateTimeFormatInfo.CurrentInfo);
        }

        /// <summary>
        /// Return a string representation of this DateTime, in the Gregorian calendarId
        /// </summary>
        /// <returns></returns>
        public string ToGregorianString()
        {
            if (this.IsNull)
            {
                return null;
            }

            return this.DateTime.ToString(DateTimeFormatInfo.CurrentInfo);
        }

        public bool IsValid()
        {
            return this.dtTicks >= 0;
        }

        /// <summary>
        /// convert to sql datetime
        /// </summary>
        /// <returns></returns>
        public SqlDateTime ToSqlDateTime()
        {
            return new SqlDateTime(this.DateTime);
        }

        public CADateTime AddYears(int years)
        {
            return new CADateTime(this.Calendar.AddYears(this.DateTime, years));
        }

        public CADateTime AddDays(int days)
        {
            return new CADateTime(this.Calendar.AddDays(this.DateTime, days));
        }

        public CADateTime AddMonths(int months)
        {
            return new CADateTime(this.Calendar.AddMonths(this.DateTime, months));
        }

        public CADateTime AddHours(int hours)
        {
            return new CADateTime(this.Calendar.AddHours(this.DateTime, hours));
        }

        public CADateTime AddMinutes(int minutes)
        {
            return new CADateTime(this.Calendar.AddMinutes(this.DateTime, minutes));
        }

        public CADateTime AddSeconds(int seconds)
        {
            return new CADateTime(this.Calendar.AddSeconds(this.DateTime, seconds));
        }

        public CADateTime AddMilliseconds(double millis)
        {
            return new CADateTime(this.Calendar.AddMilliseconds(this.DateTime, millis));
        }

        public double DiffDays(CADateTime other)
        {
            return this.DateTime.Subtract(other.DateTime).TotalDays;
        }

        public double DiffHours(CADateTime other)
        {
            return this.DateTime.Subtract(other.DateTime).TotalHours;
        }

        public double DiffMinutes(CADateTime other)
        {
            return this.DateTime.Subtract(other.DateTime).TotalMinutes;
        }

        public double DiffSeconds(CADateTime other)
        {
            return this.DateTime.Subtract(other.DateTime).TotalSeconds;
        }

        public double DiffMilliseconds(CADateTime other)
        {
            return this.DateTime.Subtract(other.DateTime).TotalMilliseconds;
        }

        // Hash and comparison operators

        public override int GetHashCode()
        {
            return this.DateTime.GetHashCode();
        }

        public override bool Equals(object obj)
        {
            if (!(obj is DateTime))
            {
                return false;
            }

            DateTime dt = (DateTime)obj;
            return this.DateTime.Equals(dt);
        }

        public XmlSchema GetSchema()
        {
            StringReader sr = new StringReader(CADateTimeSchema);
            XmlSchema schema = XmlSchema.Read(
                sr,
                new ValidationEventHandler(this.ValidationHandler));
            sr.Dispose();

            return schema;
        }

        public void ReadXml(XmlReader reader)
        {
            if (reader == null)
            {
                throw new ArgumentNullException("reader");
            }

            reader.MoveToContent();
            if (reader.GetAttribute("IsNull").Equals("true"))
            {
                this.dtTicks = CADateTime.NullTicks;
            }
            else
            {
                string calendarName = reader.GetAttribute("Calendar");
                Calendar requestedCalendar
                    = CalendarInfo.Calendars[CalendarInfo.GetCalendarId(calendarName)];

                this.dtTicks = (uint)new DateTime(
                    int.Parse(reader.GetAttribute("Year"), CultureInfo.CurrentCulture),
                    int.Parse(reader.GetAttribute("Month"), CultureInfo.CurrentCulture),
                    int.Parse(reader.GetAttribute("Day"), CultureInfo.CurrentCulture),
                    int.Parse(reader.GetAttribute("Hour"), CultureInfo.CurrentCulture),
                    int.Parse(reader.GetAttribute("Minute"), CultureInfo.CurrentCulture),
                    int.Parse(reader.GetAttribute("Second"), CultureInfo.CurrentCulture),
                    requestedCalendar).Ticks;
            }
        }

        public void WriteXml(XmlWriter writer)
        {
            if (writer == null)
            {
                throw new ArgumentNullException("writer");
            }

            writer.WriteStartElement("CADate", "http://schemas.microsoft.com/sqlserver/2004/08/CADate");
            writer.WriteAttributeString("IsNull", this.IsNull.ToString());

            if (!this.IsNull)
            {
                writer.WriteAttributeString("Year", this.Year.ToString(CultureInfo.CurrentUICulture));
                writer.WriteAttributeString("Month", this.Month.ToString(CultureInfo.CurrentUICulture));
                writer.WriteAttributeString("Day", this.Day.ToString(CultureInfo.CurrentUICulture));
                writer.WriteAttributeString("Calendar", Calendar.GetType().ToString());
            }

            writer.WriteEndElement();
        }

        // Returns a string suitable for use with string.Format which displays
        // day, month, and year components in a culture appropriate way.
        private static string DateTimeFormatString()
        {
            StringBuilder sb = new StringBuilder();
            sb.Append(CultureInfo.CurrentCulture.DateTimeFormat.ShortDatePattern);
            sb.Append(" ");
            sb.Append(CultureInfo.CurrentCulture.DateTimeFormat.LongTimePattern);
            string cultureDatePattern = sb.ToString();

            return CalendarInfo.SubstitutePositionForCharacters(datetimeChars, cultureDatePattern);
        }

      
        private void ValidationHandler(object sender, ValidationEventArgs args)
        {
            throw new ApplicationException(args.Message);
        }
    }

This is the file calendars.txt needed for defining the calendars.

; the list of calendars
; the key is the calendar ID, the value is the assembly-qualified name of the type
NumCalendars = 9

; Note, new calendars _MUST_ be added to the end of this list
0 = System.Globalization.GregorianCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089

; Saudi Hijri, the business calendar for use in Saudi Arabia
1 = System.Globalization.UmAlQuraCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089

; HijriCalendar 
2 = System.Globalization.HijriCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089

; other calendars
3 = System.Globalization.JapaneseCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089
4 = System.Globalization.JulianCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089
5 = System.Globalization.KoreanCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089
6 = System.Globalization.TaiwanCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089
7 = System.Globalization.ThaiBuddhistCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089
8 = System.Globalization.ChineseLunisolarCalendar, mscorlib, Version=2.0.3600.0, Culte=neutral, PublicKeyToken=b77a5c561934e089

; the default calendar for this culture
DefaultCalendarID = 0

This is the Transact-SQL installation script (Install.sql), which deploys the assemblies and creates the conversion functions within the database; it also crates a table of sample data.

USE AdventureWorks
GO

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ufn_CADateFromSqlDateTimeAndCalendar]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[ufn_CADateFromSqlDateTimeAndCalendar];
GO

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ufn_CADateTimeFromSqlDateTimeAndCalendar]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[ufn_CADateTimeFromSqlDateTimeAndCalendar];
GO

IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[Sales].[SalesSummary]') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)
DROP TABLE [Sales].[SalesSummary];
GO

IF EXISTS (SELECT * FROM sys.types WHERE [name] = N'CADateTime') 
DROP TYPE CADateTime;
GO

IF EXISTS (SELECT * FROM sys.types WHERE [name] = N'CADate') 
DROP TYPE CADate;
GO

-- If the assembly we want to add already exists, drop it.

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime')
DROP ASSEMBLY CADateTime;
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.neutral')
DROP ASSEMBLY [CADateTime.resources.neutral];
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.ar-SA')
DROP ASSEMBLY [CADateTime.resources.ar-SA];
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.ja')
DROP ASSEMBLY [CADateTime.resources.ja];
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.zh-CN')
DROP ASSEMBLY [CADateTime.resources.zh-CN];
GO

-- Add the assembly which contains the CLR methods we want to invoke on the server.
DECLARE @SamplesPath nvarchar(1024);
-- You may need to modify the value of the this variable if you have installed the sample someplace other than the default location.
Set @SamplesPath= N'C:\MySample\'

CREATE ASSEMBLY CADateTime
FROM @SamplesPath + 'CADateTime.dll'
WITH permission_set = safe;


CREATE ASSEMBLY [CADateTime.resources.neutral]  
FROM @SamplesPath + 'CADateTime.resources.dll'
WITH permission_set = safe;


CREATE ASSEMBLY [CADateTime.resources.ar-SA]  
FROM @SamplesPath + 'CADateTime.resources.ar-SA.dll'
WITH permission_set = safe;


CREATE ASSEMBLY [CADateTime.resources.ja]  
FROM @SamplesPath + 'CADateTime.resources.ja.dll'
WITH permission_set = safe;

CREATE ASSEMBLY [CADateTime.resources.zh-CN]  
FROM @SamplesPath + 'CADateTime.resources.zh-CN.dll'
WITH permission_set = safe;
GO

CREATE TYPE CADateTime EXTERNAL NAME CADateTime.[CADateTime];
GO

CREATE TYPE CADate EXTERNAL NAME CADateTime.[CADate];
GO

CREATE FUNCTION [dbo].[ufn_CADateFromSqlDateTimeAndCalendar]
(
    @D datetime,
    @CalendarName nvarchar(128)
) 
RETURNS CADate 
AS EXTERNAL NAME CADateTime.[CADate].FromSqlDateTimeAndCalendar;
GO

CREATE FUNCTION [dbo].[ufn_CADateTimeFromSqlDateTimeAndCalendar]
(
    @D datetime,
    @CalendarName nvarchar(128)
) 
RETURNS CADateTime
AS EXTERNAL NAME CADateTime.[CADateTime].FromSqlDateTimeAndCalendar;
GO

SELECT SalesOrderID, [dbo].[ufn_CADateTimeFromSqlDateTimeAndCalendar](OrderDate, 'GregorianCalendar') AS OrderDate, TotalDue 
INTO [Sales].[SalesSummary]
FROM [Sales].[SalesOrderHeader];
GO

ALTER TABLE [Sales].[SalesSummary] WITH CHECK ADD 
    CONSTRAINT [PK_SalesSummary_SalesOrderID] PRIMARY KEY CLUSTERED 
    (
        [SalesOrderID]
    );
GO


ALTER TABLE [Sales].[SalesSummary] ADD DayOfYear AS [OrderDate].[Day] PERSISTED;
GO
 
CREATE INDEX IX_Sales_SalesSummary ON [Sales].[SalesSummary] (DayOfYear);
GO

This is test.sql, which tests the sample by executing the functions on various calendars.

USE AdventureWorks
GO

SELECT CADateTime::CurrentCalendarName;

-- Simple usage, create a new value from a string and print it out
-- We're using ISO 8601 format dates as input, which are YYYY-MM-DD
DECLARE @h CADateTime;
SET @h = '1976-01-02';
SELECT CAST(@h as nvarchar(128)), @h.CalendarName;
GO

-- print it out in "full format"
DECLARE @h CADateTime;
SET @h = '1976-01-02';
SELECT @h.ToGregorianStringUsingFormat('F');
GO

-- print it out in a custom format
DECLARE @h CADateTime;
SET @h = '1976-01-02';
SELECT @h.ToGregorianStringUsingFormat('MMM dd yyyy');
GO

-- convert it to arabic (for testing purposes)
DECLARE @h CADateTime;
SET @h = CADateTime::Parse('1976-01-02');
SELECT @h.ToString(), @h.ToGregorianStringUsingFormat('F');
GO

-- convert sql datetime to CAD and back
DECLARE @h CADateTime;
SET @h = CADateTime::FromSqlDateTime(GetDate());
SELECT @h.ToString(), @h.ToSqlDateTime();
GO

-- get the current CAD, in two ways
SELECT   CADateTime::Now.ToString(), 
    CADateTime::FromSqlDateTime(GetDate()).ToString();
GO

-- do some arithmetic
DECLARE @h CADateTime, @d datetime;
SET @h = CADateTime::Now; -- get the current hijri datetime
SET @h = @h.AddDays(10); -- add ten days to it
SET @d = GetDate(); -- current sql date
SET @d = DateAdd(day, 10, @d); -- add ten days to the sql datetime
-- print 'em both, should be the same
SELECT @h.ToSqlDateTime(), @d;
GO

-- what about datepart
DECLARE @h CADateTime;
SET @h = CADateTime::Now; -- get the current datetime
SELECT @h.Year as year, @h.Month as month, @h.Day as dayofyear, @h.DayOfMonth as dom;
GO

-- print the same date in four different calendars
SELECT 
    CADateTime::FromSqlDateTimeAndCalendar(GetDate(), 'UmAlQuraCalendar').ToString() as Umq,
    CADateTime::FromSqlDateTimeAndCalendar(GetDate(), 'GregorianCalendar').ToString() as Gregorian,
    CADateTime::FromSqlDateTimeAndCalendar(GetDate(), 'JapaneseCalendar').ToString() as Japanese,
    CADateTime::FromSqlDateTimeAndCalendar(GetDate(), 'ChineseLunisolarCalendar').ToString() as ChineseLunisolar;
GO

SELECT CADate::CurrentCalendarName;

-- simple usage, create a new value from a string and print it out
DECLARE @h CADate;
SET @h = '1976-01-02';
SELECT CAST(@h as nvarchar(128)), @h.CalendarName;
GO

-- print it out in "date format"
DECLARE @h CADate;
SET @h = '1976-01-02';
SELECT @h.ToGregorianStringUsingFormat('d');
GO

-- print it out in a custom format
DECLARE @h CADate;
SET @h = '1976-01-02';
SELECT @h.ToGregorianStringUsingFormat('MMM dd yyyy');
GO

-- convert it to arabic (for testing purposes)
DECLARE @h CADate;
SET @h = CADate::Parse('1976-01-02');
SELECT @h.ToString(), @h.ToGregorianStringUsingFormat('d');
GO

-- convert sql datetime to CAD and back
DECLARE @h CADate;
SET @h = CADate::FromSqlDateTime(GetDate());
SELECT @h.ToString(), @h.ToSqlDateTime();
GO

-- get the current CAD, in two ways
SELECT   CADate::Now.ToString(), 
    CADate::FromSqlDateTime(GetDate()).ToString();
GO

-- do some arithmetic
DECLARE @h CADate, @d datetime;
SET @h = CADate::Now; -- get the current hijri datetime
SET @h = @h.AddDays(10); -- add ten days to it
SET @d = GetDate(); -- current sql date
SET @d = DateAdd(day, 10, @d); -- add ten days to the sql datetime
-- print 'em both, should be the same
SELECT @h.ToSqlDateTime(), @d;
GO

-- what about datepart
DECLARE @h CADate;
SET @h = CADate::Now; -- get the current datetime
SELECT @h.Year as year, @h.Month as month, @h.Day as dayofyear, @h.DayOfMonth as dom;
GO

-- print the same date in four different calendars
SELECT 
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'UmAlQuraCalendar').ToString() as Umq,
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'GregorianCalendar').ToString() as Gregorian,
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'JapaneseCalendar').ToString() as Japanese,
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'ChineseLunisolarCalendar').ToString() as ChineseLunisolar;
GO

-- Show the total sales figures for particular days of the year over a 90 day 
-- range starting with day 90.
SELECT DayOfYear, SUM(TotalDue)
FROM [Sales].[SalesSummary]
WHERE DayOfYear >= 90 AND DayOfYear < 180
GROUP BY DayOfYear
ORDER BY DayOfYear;
GO

-- Show the first day of the year where there is sales between day 90 and day 180.
SELECT TOP 1 DayOfYear 
FROM [Sales].[SalesSummary]
WHERE DayOfYear >= 90 AND DayOfYear < 180 
ORDER BY DayOfYear ASC
GO

SET LANGUAGE French
GO

-- print the same date in four different calendars using the French culture
SELECT 
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'UmAlQuraCalendar').ToString() as Umq,
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'GregorianCalendar').ToString() as Gregorian,
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'JapaneseCalendar').ToString() as Japanese,
    CADate::FromSqlDateTimeAndCalendar(GetDate(), 'ChineseLunisolarCalendar').ToString() as ChineseLunisolar;
GO

SET LANGUAGE us_english
GO

The following Transact-SQL removes the assemblies, functions and table from the database.

USE AdventureWorks
GO

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ufn_CADateFromSqlDateTimeAndCalendar]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[ufn_CADateFromSqlDateTimeAndCalendar];
GO

IF EXISTS (SELECT * FROM sys.objects WHERE object_id = OBJECT_ID(N'[dbo].[ufn_CADateTimeFromSqlDateTimeAndCalendar]') AND type in (N'FN', N'IF', N'TF', N'FS', N'FT'))
DROP FUNCTION [dbo].[ufn_CADateTimeFromSqlDateTimeAndCalendar];
GO

IF EXISTS (SELECT * FROM dbo.sysobjects WHERE id = OBJECT_ID(N'[Sales].[SalesSummary]') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)
DROP TABLE [Sales].[SalesSummary];
GO

IF EXISTS (SELECT * FROM sys.types WHERE [name] = N'CADateTime') 
DROP TYPE CADateTime;
GO

IF EXISTS (SELECT * FROM sys.types WHERE [name] = N'CADate') 
DROP TYPE CADate;
GO

-- If the assembly we want to add already exists, drop it.

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime')
DROP ASSEMBLY CADateTime;
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.neutral')
DROP ASSEMBLY [CADateTime.resources.neutral];
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.ar-SA')
DROP ASSEMBLY [CADateTime.resources.ar-SA];
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.ja')
DROP ASSEMBLY [CADateTime.resources.ja];
GO

IF EXISTS (SELECT [name] FROM sys.assemblies WHERE [name] = N'CADateTime.resources.zh-CN')
DROP ASSEMBLY [CADateTime.resources.zh-CN];
GO

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