CalendarWeekRule Enumeration
Assembly: mscorlib (in mscorlib.dll)
'Declaration <SerializableAttribute> _ <ComVisibleAttribute(True)> _ Public Enumeration CalendarWeekRule 'Usage Dim instance As CalendarWeekRule
/** @attribute SerializableAttribute() */ /** @attribute ComVisibleAttribute(true) */ public enum CalendarWeekRule
SerializableAttribute ComVisibleAttribute(true) public enum CalendarWeekRule
| Member name | Description | |
|---|---|---|
![]() | FirstDay | Indicates that the first week of the year starts on the first day of the year and ends before the following designated first day of the week. The value is 0. |
![]() | FirstFourDayWeek | Indicates that the first week of the year is the first week with four or more days before the designated first day of the week. Complies with ISO 8601. The value is 2. |
![]() | FirstFullWeek | Indicates that the first week of the year begins on the first occurrence of the designated first day of the week on or after the first day of the year. The value is 1. |
These calendar week rules depend on the System.DayOfWeek value that is designated as the first day of the week. The DateTimeFormatInfo.FirstDayOfWeek property provides the default value for a culture, but any DayOfWeek value can be specified as the first day of the week in the Calendar.GetWeekOfYear method.
The first week based on the FirstDay value can have one to seven days. The first week based on the FirstFullWeek value always has seven days. The first week based on the FirstFourDayWeek value can have four to seven days.
For example, in the Gregorian calendar, suppose that the first day of the year (January 1) falls on a Tuesday and the designated first day of the week is Sunday. Selecting FirstFullWeek defines the first Sunday (January 6) as the beginning of the first week of the year. The first five days of the year are considered part of the last week of the previous year. In contrast, selecting FirstFourDayWeek defines the first day of the year (January 1) as the beginning of the first week of the year because there are more than four days from January 1 to the day before the following Sunday.
| Date | FirstDay | FirstFullWeek | FirstFourDayWeek |
|---|---|---|---|
| Dec 31 Mon | Last week of the previous year | Last week of the previous year | Last week of the previous year |
| Jan 1 Tue | Week 1 | Last week of the previous year | Week 1 |
| Jan 2 Wed | Week 1 | Last week of the previous year | Week 1 |
| Jan 3 Thu | Week 1 | Last week of the previous year | Week 1 |
| Jan 4 Fri | Week 1 | Last week of the previous year | Week 1 |
| Jan 5 Sat | Week 1 | Last week of the previous year | Week 1 |
| Jan 6 Sun | Week 2 | Week 1 | Week 2 |
| Jan 7 Mon | Week 2 | Week 1 | Week 2 |
| Jan 8 Tue | Week 2 | Week 1 | Week 2 |
| Jan 9 Wed | Week 2 | Week 1 | Week 2 |
| Jan 10 Thu | Week 2 | Week 1 | Week 2 |
| Jan 11 Fri | Week 2 | Week 1 | Week 2 |
| Jan 12 Sat | Week 2 | Week 1 | Week 2 |
Suppose the first day of the year (January 1) falls on a Friday and the designated first day of the week is Sunday. Selecting FirstFourDayWeek defines the first Sunday (January 3) as the beginning of the first week of the year because there are fewer than four days from January 1 to the day before the following Sunday.
| Date | FirstDay | FirstFullWeek | FirstFourDayWeek |
|---|---|---|---|
| Dec 31 Thu | Last week of the previous year | Last week of the previous year | Last week of the previous year |
| Jan 1 Fri | Week 1 | Last week of the previous year | Last week of the previous year |
| Jan 2 Sat | Week 1 | Last week of the previous year | Last week of the previous year |
| Jan 3 Sun | Week 2 | Week 1 | Week 1 |
| Jan 4 Mon | Week 2 | Week 1 | Week 1 |
| Jan 5 Tue | Week 2 | Week 1 | Week 1 |
| Jan 6 Wed | Week 2 | Week 1 | Week 1 |
| Jan 7 Thu | Week 2 | Week 1 | Week 1 |
| Jan 8 Fri | Week 2 | Week 1 | Week 1 |
| Jan 9 Sat | Week 2 | Week 1 | Week 1 |
Each CultureInfo supports a set of calendars. The Calendar property returns the default calendar for the culture, and the OptionalCalendars property returns an array containing all the calendars supported by the culture. To change the calendar used by a CultureInfo, set the Calendar property of CultureInfo.DateTimeFormat to a new Calendar.
Note |
|---|
| To create a calendar that complies with ISO 8601, use FirstFourDayWeek. |
Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.
