TimeZoneInfo.GetSystemTimeZones Method

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Overloads

GetSystemTimeZones()	Returns a sorted collection of all the time zones about which information is available on the local system.
GetSystemTimeZones(Boolean)	Returns a ReadOnlyCollection<T> containing all valid TimeZone's from the local machine. This method does not throw TimeZoneNotFoundException or InvalidTimeZoneException.

GetSystemTimeZones()

Source:

TimeZoneInfo.cs

Returns a sorted collection of all the time zones about which information is available on the local system.

public:
 static System::Collections::ObjectModel::ReadOnlyCollection<TimeZoneInfo ^> ^ GetSystemTimeZones();

public static System.Collections.ObjectModel.ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones ();

static member GetSystemTimeZones : unit -> System.Collections.ObjectModel.ReadOnlyCollection<TimeZoneInfo>

Public Shared Function GetSystemTimeZones () As ReadOnlyCollection(Of TimeZoneInfo)

Returns

ReadOnlyCollection<TimeZoneInfo>

A read-only collection of TimeZoneInfo objects.

Exceptions

OutOfMemoryException

There is insufficient memory to store all time zone information.

SecurityException

The user does not have permission to read from the registry keys that contain time zone information.

Examples

The following example retrieves a collection of time zone objects that represent the time zones defined on a computer and writes information about them to a text file.

using System;
using System.Globalization;
using System.IO;
using System.Collections.ObjectModel;

public class Example
{
   public static void Main()
   {
      const string OUTPUTFILENAME = @"C:\Temp\TimeZoneInfo.txt";
   
      DateTimeFormatInfo dateFormats = CultureInfo.CurrentCulture.DateTimeFormat;
      ReadOnlyCollection<TimeZoneInfo> timeZones = TimeZoneInfo.GetSystemTimeZones(); 
      StreamWriter sw = new StreamWriter(OUTPUTFILENAME, false);
   
      foreach (TimeZoneInfo timeZone in timeZones)
      {
         bool hasDST = timeZone.SupportsDaylightSavingTime;
         TimeSpan offsetFromUtc = timeZone.BaseUtcOffset;
         TimeZoneInfo.AdjustmentRule[] adjustRules;
         string offsetString;
      
         sw.WriteLine("ID: {0}", timeZone.Id);
         sw.WriteLine("   Display Name: {0, 40}", timeZone.DisplayName);
         sw.WriteLine("   Standard Name: {0, 39}", timeZone.StandardName);
         sw.Write("   Daylight Name: {0, 39}", timeZone.DaylightName);
         sw.Write(hasDST ? "   ***Has " : "   ***Does Not Have ");
         sw.WriteLine("Daylight Saving Time***");
         offsetString = String.Format("{0} hours, {1} minutes", offsetFromUtc.Hours, offsetFromUtc.Minutes);
         sw.WriteLine("   Offset from UTC: {0, 40}", offsetString);
         adjustRules = timeZone.GetAdjustmentRules();
         sw.WriteLine("   Number of adjustment rules: {0, 26}", adjustRules.Length);  
         if (adjustRules.Length > 0)
         {
            sw.WriteLine("   Adjustment Rules:");
            foreach (TimeZoneInfo.AdjustmentRule rule in adjustRules)
            {
               TimeZoneInfo.TransitionTime transTimeStart = rule.DaylightTransitionStart;
               TimeZoneInfo.TransitionTime transTimeEnd = rule.DaylightTransitionEnd; 
            
               sw.WriteLine("      From {0} to {1}", rule.DateStart, rule.DateEnd);
               sw.WriteLine("      Delta: {0}", rule.DaylightDelta);
               if (!transTimeStart.IsFixedDateRule)
               {
                  sw.WriteLine("      Begins at {0:t} on {1} of week {2} of {3}", transTimeStart.TimeOfDay, 
                                                                                transTimeStart.DayOfWeek,                                                                                 
                                                                                transTimeStart.Week, 
                                                                                dateFormats.MonthNames[transTimeStart.Month - 1]);
                  sw.WriteLine("      Ends at {0:t} on {1} of week {2} of {3}", transTimeEnd.TimeOfDay,
                                                                                transTimeEnd.DayOfWeek, 
                                                                                transTimeEnd.Week,
                                                                                dateFormats.MonthNames[transTimeEnd.Month - 1]);
               }
               else
               {
                  sw.WriteLine("      Begins at {0:t} on {1} {2}", transTimeStart.TimeOfDay, 
                                                                 transTimeStart.Day, 
                                                                 dateFormats.MonthNames[transTimeStart.Month - 1]);
                  sw.WriteLine("      Ends at {0:t} on {1} {2}", transTimeEnd.TimeOfDay, 
                                                               transTimeEnd.Day, 
                                                               dateFormats.MonthNames[transTimeEnd.Month - 1]);
               }
            }
         }            
      }
      sw.Close();
   }
}

open System
open System.Globalization
open System.IO
open System.Collections.ObjectModel

[<EntryPoint>]
let main _ =
    let OUTPUTFILENAME = @"C:\Temp\TimeZoneInfo.txt"

    let dateFormats = CultureInfo.CurrentCulture.DateTimeFormat
    let timeZones = TimeZoneInfo.GetSystemTimeZones() 
    use sw = new StreamWriter(OUTPUTFILENAME, false)

    for timeZone in timeZones do
        let hasDST = timeZone.SupportsDaylightSavingTime
        let offsetFromUtc = timeZone.BaseUtcOffset
    
        sw.WriteLine $"ID: {timeZone.Id}"
        sw.WriteLine $"   Display Name: {timeZone.DisplayName, 40}"
        sw.WriteLine $"   Standard Name: {timeZone.StandardName, 39}"
        sw.Write $"   Daylight Name: {timeZone.DaylightName, 39}"
        sw.Write(if hasDST then "   ***Has " else "   ***Does Not Have ")
        sw.WriteLine "Daylight Saving Time***"
        let offsetString = $"{offsetFromUtc.Hours} hours, {offsetFromUtc.Minutes} minutes"
        sw.WriteLine $"   Offset from UTC: {offsetString, 40}"
        let adjustRules = timeZone.GetAdjustmentRules()
        sw.WriteLine $"   Number of adjustment rules: {adjustRules.Length, 26}"
        if adjustRules.Length > 0 then
            sw.WriteLine "   Adjustment Rules:"
            for rule in adjustRules do
                let transTimeStart = rule.DaylightTransitionStart
                let transTimeEnd = rule.DaylightTransitionEnd 
            
                sw.WriteLine $"      From {rule.DateStart} to {rule.DateEnd}"
                sw.WriteLine $"      Delta: {rule.DaylightDelta}"
                if not transTimeStart.IsFixedDateRule then
                    sw.WriteLine $"      Begins at {transTimeStart.TimeOfDay:t} on {transTimeStart.DayOfWeek} of week {transTimeStart.Week} of {dateFormats.MonthNames[transTimeStart.Month - 1]}"
                    sw.WriteLine $"      Ends at {transTimeEnd.TimeOfDay:t} on {transTimeEnd.DayOfWeek} of week {transTimeEnd.Week} of {dateFormats.MonthNames[transTimeEnd.Month - 1]}"
                else
                    sw.WriteLine $"      Begins at {transTimeStart.TimeOfDay:t} on {transTimeStart.Day} {dateFormats.MonthNames[transTimeStart.Month - 1]}"
                    sw.WriteLine $"      Ends at {transTimeEnd.TimeOfDay:t} on {transTimeEnd.Day} {dateFormats.MonthNames[transTimeEnd.Month - 1]}"
    0

Imports System.Collections.ObjectModel
Imports System.Globalization
Imports System.IO

Module Example
   Public Sub Main()
      Const OUTPUTFILENAME As String = "C:\Temp\TimeZoneInfo.txt"
      
      Dim timeZones As ReadOnlyCollection(Of TimeZoneInfo) = TimeZoneInfo.GetSystemTimeZones() 
      Dim sw As StreamWriter = New StreamWriter(OUTPUTFILENAME, False)
      
      For Each timeZone As TimeZoneInfo in timeZones
         Dim hasDST As Boolean = timeZone.SupportsDaylightSavingTime
         Dim offsetFromUtc As TimeSpan = timeZone.BaseUtcOffset
         Dim adjustRules() As System.TimeZoneInfo.AdjustmentRule
         Dim offsetString As String
         
         sw.WriteLine("ID: {0}", timeZone.Id)
         sw.WriteLine("   Display Name: {0, 40}", timeZone.DisplayName)
         sw.WriteLine("   Standard Name: {0, 39}", timeZone.StandardName)
         sw.Write("   Daylight Name: {0, 39}", timeZone.DaylightName)
         sw.Write(iif(hasDST, "   ***Has ", "   ***Does Not Have "))
         sw.WriteLine("Daylight Saving Time***")
         offsetString = String.Format("{0} hours, {1} minutes", offsetFromUtc.Hours, offsetFromUtc.Minutes)
         sw.WriteLine("   Offset from UTC: {0, 40}", offsetString)
         adjustRules = timeZone.GetAdjustmentRules()
         sw.WriteLine("   Number of adjustment rules: {0, 26}", adjustRules.Length)  
         If adjustRules.Length > 0 Then
            sw.WriteLine("   Adjustment Rules:")
            For Each rule As TimeZoneInfo.AdjustmentRule In adjustRules
               Dim transTimeStart As TimeZoneInfo.TransitionTime = rule.DaylightTransitionStart
               Dim transTimeEnd As TimeZoneInfo.TransitionTime = rule.DaylightTransitionEnd 
               
               sw.WriteLine("      From {0} to {1}", rule.DateStart, rule.DateEnd)
               sw.WriteLine("      Delta: {0}", rule.DaylightDelta)
               If Not transTimeStart.IsFixedDateRule
                  sw.WriteLine("      Begins at {0:t} on {1} of week {2} of {3}", transTimeStart.TimeOfDay, _
                                                                                transTimeStart.DayOfWeek, _
                                                                                transTimeStart.Week, _
                                                                                MonthName(transTimeStart.Month))
                  sw.WriteLine("      Ends at {0:t} on {1} of week {2} of {3}", transTimeEnd.TimeOfDay, _
                                                                                transTimeEnd.DayOfWeek, _
                                                                                transTimeEnd.Week, _
                                                                                MonthName(transTimeEnd.Month))
               Else
                  sw.WriteLine("      Begins at {0:t} on {1} {2}", transTimeStart.TimeOfDay, _
                                                                 transTimeStart.Day, _
                                                                 MonthName(transTimeStart.Month))
                  sw.WriteLine("      Ends at {0:t} on {1} {2}", transTimeEnd.TimeOfDay, _
                                                               transTimeEnd.Day, _
                                                               MonthName(transTimeEnd.Month))
               End If
            Next
         End If            
      Next
      sw.Close()

#  Get timezone/date details and open a stream writer
$DateFormats    = [System.Globalization.CultureInfo]::CurrentCulture.DateTimeFormat
$TimeZones      = [System.TimeZoneInfo]::GetSystemTimeZones()
$OutputFileName = 'C:\Temp\TimeZoneInfo.txt'
$Sw             = New-Object -TypeName System.IO.StreamWriter -ArgumentList $OutputFileName,$false
# Write overview information
$Sw.WriteLine('{0} Time zones on this system' -f $TimeZones.Count)

# Process each timezone on the system
# Write details to the streamwriter
foreach ($TimeZone in $TimeZones) {
 $HasDST        = $TimeZone.SupportsDaylightSavingTime
 $OffsetFromUtc = $TimeZone.BaseUtcOffset
 $Sw.WriteLine("ID: {0}" -f $TimeZone.Id)
 $Sw.WriteLine("   Display Name:  {0}" -f $TimeZone.DisplayName)
 $Sw.WriteLine("   Standard Name: {0}" -f $TimeZone.StandardName)
 $Sw.Write("   Daylight Name: {0}" -f $TimeZone.DaylightName)
 $Sw.Write( $(If ($HasDST) {"  ***Has: "} Else {"  ***Does Not Have: "}))
 $Sw.WriteLine("Daylight Saving Time***")
 $OffsetString = "{0} hours, {1} minutes" -f $OffsetFromUtc.Hours, $OffsetFromUtc.Minutes
 $Sw.WriteLine("   Offset from UTC: {0}"  -f $offsetString)
 $AdjustRules = $timeZone.GetAdjustmentRules()
 $Sw.WriteLine("   Number of adjustment rules: {0}" -f $adjustRules.Count)
 If ($AdjustRules.Count -gt 0)
 {
    $Sw.WriteLine("   Adjustment Rules:")
    foreach ($Rule in $AdjustRules)
    {
       $TransTimeStart = $Rule.DaylightTransitionStart
       $TransTimeEnd   = $Rule.DaylightTransitionEnd
       $Sw.WriteLine(("     From   {0} to {1}" -f $Rule.DateStart, $Rule.DateEnd))
       $Sw.WriteLine(("       Delta: {0}" -f $Rule.DaylightDelta))
       if (-Not  $TransTimeStart.IsFixedDateRule)
       {
          $Sw.WriteLine(("       Begins at {0:t} on {1} of week {2} of {3}" -f $TransTimeStart.TimeOfDay, 
                                                                             $TransTimeStart.DayOfWeek,                                                                                 
                                                                             $TransTimeStart.Week, 
                                                                             $DateFormats.MonthNames[$TransTimeStart.Month - 1]))
          $Sw.WriteLine(("       Ends at {0:t} on {1} of week {2} of {3}" -f $TransTimeEnd.TimeOfDay,
                                                                             $TransTimeEnd.DayOfWeek, 
                                                                             $TransTimeEnd.Week,
                                                                             $DateFormats.MonthNames[[int] $TransTimeEnd.Month - 1]))
       }
     else
       {
         $Sw.WriteLine(("       Begins at {0:t} on {1} {2}" -f $TransTimeStart.TimeOfDay, 
                                                             $TransTimeStart.Day, 
                                                             $DateFormats.MonthNames[$transTimeStart.Month - 1]))
         $Sw.WriteLine(("       Ends at {0:t} on {1} {2}"   -f $TransTimeEnd.TimeOfDay, 
                                                             $TransTimeEnd.Day, 
                                                             $DateFormats.MonthNames[$transTimeEnd.Month - 1]))        
       }
    } # End of processing each adjustment rule
 } # End of checking adjustment rules
} # End of processing Time Zones

# Close stream writer then display output in notepad
$Sw.Close() 

#  Output of 1st three time zones:
#  135 Time zones on this system
#  ID: Dateline Standard Time
#     Display Name:  (UTC-12:00) International Date Line West
#     Standard Name: Dateline Standard Time
#     Daylight Name: Dateline Summer Time  ***Does Not Have: Daylight Saving Time***
#     Offset from UTC: -12 hours, 0 minutes
#     Number of adjustment rules: 0
#  ID: UTC-11
#     Display Name:  (UTC-11:00) Co-ordinated Universal Time-11
#     Standard Name: UTC-11
#     Daylight Name: UTC-11  ***Does Not Have: Daylight Saving Time***
#     Offset from UTC: -11 hours, 0 minutes
#     Number of adjustment rules: 0
#  ID: Aleutian Standard Time
#     Display Name:  (UTC-10:00) Aleutian Islands
#     Standard Name: Aleutian Standard Time
#     Daylight Name: Aleutian Summer Time  ***Has: Daylight Saving Time***
#     Offset from UTC: -10 hours, 0 minutes
#     Number of adjustment rules: 2
#     Adjustment Rules:
#       From   01/01/0001 00:00:00 to 31/12/2006 00:00:00
#         Delta: 01:00:00
#         Begins at 02:00 on Sunday of week 1 of April
#         Ends at 02:00 on Sunday of week 5 of October
#       From   01/01/2007 00:00:00 to 31/12/9999 00:00:00
#         Delta: 01:00:00
#         Begins at 02:00 on Sunday of week 2 of March
#         Ends at 02:00 on Sunday of week 1 of November

Remarks

The GetSystemTimeZones method retrieves all available time zone information from the subkeys of the registry's HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Time Zones key on Windows systems and from the ICU Library on Linux and macOS. If it is unable to successfully retrieve and parse values for particular string properties of individual TimeZoneInfo objects, this method sets their value to an empty string ("").

Important

The GetSystemTimeZones method returns a collection of TimeZoneInfo objects only for time zones defined in the Windows registry or the ICU library. It does not include time zones created using the overloads of the CreateCustomTimeZone method. These are accessible only through the object reference returned by the time zone creation method.

The collection returned by this method is sorted by UTC offset and, for time zones that have the same UTC offset, by the display name using the current culture. For information about the display name, see DisplayName.

The ReadOnlyCollection<T> object returned by this method supports the IEnumerable<T> interface, which means that it can be iterated using the foreach (in C#) or For Each…Next (in Visual Basic) statements. Each iteration of the loop provides the next TimeZoneInfo object in the collection.

The collection of TimeZoneInfo objects represents time zones defined on the local computer; it does not necessarily provide complete information for all time zones during all time periods. If your application requires time zones not found on the local computer, you can create custom time zones using the overloads of the CreateCustomTimeZone method. For more information, see How to: Create Time Zones Without Adjustment Rules and How to: Create Time Zones with Adjustment Rules.

You can also determine whether an individual time zone is defined on the local computer by calling the FindSystemTimeZoneById method and providing the identifier of the time zone you want to retrieve as a parameter.

GetSystemTimeZones(Boolean)

Source:

TimeZoneInfo.cs

Returns a ReadOnlyCollection<T> containing all valid TimeZone's from the local machine. This method does not throw TimeZoneNotFoundException or InvalidTimeZoneException.

public:
 static System::Collections::ObjectModel::ReadOnlyCollection<TimeZoneInfo ^> ^ GetSystemTimeZones(bool skipSorting);

public static System.Collections.ObjectModel.ReadOnlyCollection<TimeZoneInfo> GetSystemTimeZones (bool skipSorting);

static member GetSystemTimeZones : bool -> System.Collections.ObjectModel.ReadOnlyCollection<TimeZoneInfo>

Public Shared Function GetSystemTimeZones (skipSorting As Boolean) As ReadOnlyCollection(Of TimeZoneInfo)

Parameters

skipSorting

Boolean

If true, The collection returned may not necessarily be sorted.

Returns

ReadOnlyCollection<TimeZoneInfo>

Remarks

By setting the skipSorting parameter to true, the method will attempt to avoid sorting the returned collection. This option can be beneficial when the caller does not require a sorted list and aims to enhance the performance.