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TimeZoneInfo.GetAdjustmentRules Method

Retrieves an array of TimeZoneInfo.AdjustmentRule objects that apply to the current TimeZoneInfo object.

Namespace:  System
Assembly:  System.Core (in System.Core.dll)

public TimeZoneInfo..::.AdjustmentRule[] GetAdjustmentRules()

Return Value

Type: System.TimeZoneInfo.AdjustmentRule[]
An array of TimeZoneInfo.AdjustmentRule objects for this time zone.

ExceptionCondition
OutOfMemoryException

The system does not have enough memory to make an in-memory copy of the adjustment rules.

The GetAdjustmentRules method retrieves an array of System.TimeZoneInfo.AdjustmentRule objects. Each object in the array defines the effective start and end date of that time zone adjustment, as well as its delta (the exact amount by which the adjustment causes the time to change). In addition, two properties return System.TimeZoneInfo.TransitionTime objects that define when each annual transition to and from standard time occurs.

If a time zone has no adjustment rules, the GetAdjustmentRules method returns an empty array (an array whose Length is zero).

Any modifications to the elements of the array returned by the GetAdjustmentRules method are not reflected in the adjustment rules that belong to a particular time zone. To modify a time zone's adjustment rules (such as to reflect its historical transition to and from daylight saving time) you must create a new time zone with the appropriate adjustment rules, rather than modify the existing one.

The following example retrieves all time zones that are defined on the local system and displays complete information about their adjustment rules to the console.

private enum WeekOfMonth 
{
   First = 1,
   Second = 2,
   Third = 3,
   Fourth = 4,
   Last = 5,
}

private static void ShowStartAndEndDates()
{
   // Get all time zones from system
   ReadOnlyCollection<TimeZoneInfo> timeZones = TimeZoneInfo.GetSystemTimeZones();
   string[] monthNames = CultureInfo.CurrentCulture.DateTimeFormat.MonthNames;
   // Get each time zone 
   foreach (TimeZoneInfo timeZone in timeZones)
   {
      TimeZoneInfo.AdjustmentRule[] adjustments = timeZone.GetAdjustmentRules();
      // Display message for time zones with no adjustments 
      if (adjustments.Length == 0)
      {
         Console.WriteLine("{0} has no adjustment rules", timeZone.StandardName);
      }   
      else
      {
         // Handle time zones with 1 or 2+ adjustments differently 
         bool showCount = false;
         int ctr = 0;
         string spacer = "";

         Console.WriteLine("{0} Adjustment rules", timeZone.StandardName);
         if (adjustments.Length > 1)
         {
            showCount = true;
            spacer = "   ";
         }   
         // Iterate adjustment rules 
         foreach (TimeZoneInfo.AdjustmentRule adjustment in adjustments)
         {
            if (showCount)
            { 
               Console.WriteLine("   Adjustment rule #{0}", ctr+1);
               ctr++;
            }
            // Display general adjustment information
            Console.WriteLine("{0}   Start Date: {1:D}", spacer, adjustment.DateStart);
            Console.WriteLine("{0}   End Date: {1:D}", spacer, adjustment.DateEnd);
            Console.WriteLine("{0}   Time Change: {1}:{2:00} hours", spacer, 
                              adjustment.DaylightDelta.Hours, adjustment.DaylightDelta.Minutes);
            // Get transition start information
            TimeZoneInfo.TransitionTime transitionStart = adjustment.DaylightTransitionStart;
            Console.Write("{0}   Annual Start: ", spacer);
            if (transitionStart.IsFixedDateRule)
            {
               Console.WriteLine("On {0} {1} at {2:t}", 
                                 monthNames[transitionStart.Month - 1], 
                                 transitionStart.Day, 
                                 transitionStart.TimeOfDay);
            }
            else
            {
               Console.WriteLine("The {0} {1} of {2} at {3:t}", 
                                 ((WeekOfMonth)transitionStart.Week).ToString(), 
                                 transitionStart.DayOfWeek.ToString(), 
                                 monthNames[transitionStart.Month - 1], 
                                 transitionStart.TimeOfDay);
            }
            // Get transition end information
            TimeZoneInfo.TransitionTime transitionEnd = adjustment.DaylightTransitionEnd;
            Console.Write("{0}   Annual End: ", spacer);
            if (transitionEnd.IsFixedDateRule)
            {
               Console.WriteLine("On {0} {1} at {2:t}", 
                                 monthNames[transitionEnd.Month - 1], 
                                 transitionEnd.Day, 
                                 transitionEnd.TimeOfDay);
            }
            else
            {
               Console.WriteLine("The {0} {1} of {2} at {3:t}", 
                                 ((WeekOfMonth)transitionEnd.Week).ToString(), 
                                 transitionEnd.DayOfWeek.ToString(), 
                                 monthNames[transitionEnd.Month - 1], 
                                 transitionEnd.TimeOfDay);
            }
         }
      }   
      Console.WriteLine();
   } 
}

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5

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