TimeZoneInfo.GetAdjustmentRules Method
Definition
Important
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Retrieves an array of TimeZoneInfo.AdjustmentRule objects that apply to the current TimeZoneInfo object.
public:
cli::array <TimeZoneInfo::AdjustmentRule ^> ^ GetAdjustmentRules();public TimeZoneInfo.AdjustmentRule[] GetAdjustmentRules ();member this.GetAdjustmentRules : unit -> TimeZoneInfo.AdjustmentRule[]Public Function GetAdjustmentRules () As TimeZoneInfo.AdjustmentRule()Returns
An array of objects for this time zone.
Exceptions
The system does not have enough memory to make an in-memory copy of the adjustment rules.
Examples
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();
}
}
type WeekOfMonth =
| First = 1
| Second = 2
| Third = 3
| Fourth = 4
| Last = 5
let showStartAndEndDates () =
// Get all time zones from system
let timeZones = TimeZoneInfo.GetSystemTimeZones()
let monthNames = CultureInfo.CurrentCulture.DateTimeFormat.MonthNames
// Get each time zone
for timeZone in timeZones do
let adjustments = timeZone.GetAdjustmentRules()
// Display message for time zones with no adjustments
if adjustments.Length = 0 then
printfn $"{timeZone.StandardName} has no adjustment rules"
else
// Handle time zones with 1 or 2+ adjustments differently
let mutable ctr = 0
let showCount, spacer =
if adjustments.Length > 1 then
true, " "
else
false, ""
printfn $"{timeZone.StandardName} Adjustment rules"
// Iterate adjustment rules
for adjustment in adjustments do
if showCount then
printfn $" Adjustment rule #{ctr + 1}"
ctr <- ctr + 1
// Display general adjustment information
printfn $"{spacer} Start Date: {adjustment.DateStart:D}"
printfn $"{spacer} End Date: {adjustment.DateEnd:D}"
printfn $"{spacer} Time Change: {adjustment.DaylightDelta.Hours}:{adjustment.DaylightDelta.Minutes:D2} hours"
// Get transition start information
let transitionStart = adjustment.DaylightTransitionStart
printf $"{spacer} Annual Start: "
if transitionStart.IsFixedDateRule then
printfn $"On {monthNames[transitionStart.Month - 1]} {transitionStart.Day} at {transitionStart.TimeOfDay:t}"
else
printfn $"The {transitionStart.Week |> enum<WeekOfMonth>} {transitionStart.DayOfWeek} of {monthNames[transitionStart.Month - 1]} at {transitionStart.TimeOfDay:t}"
// Get transition end information
let transitionEnd = adjustment.DaylightTransitionEnd
printf $"{spacer} Annual End: "
if transitionEnd.IsFixedDateRule then
printfn $"On {monthNames[transitionEnd.Month - 1]} {transitionEnd.Day} at {transitionEnd.TimeOfDay:t}"
else
printfn $"The {enum<WeekOfMonth> transitionEnd.Week} {transitionEnd.DayOfWeek} of {monthNames[transitionEnd.Month - 1]} at {transitionEnd.TimeOfDay:t}"
Console.WriteLine()
Private Enum WeekOfMonth As Integer
First = 1
Second = 2
Third = 3
Fourth = 4
Last = 5
End Enum
Private Sub ShowStartAndEndDates()
' Get all time zones from system
Dim timeZones As ReadOnlyCollection(Of TimeZoneInfo) = TimeZoneInfo.GetSystemTimeZones()
' Get each time zone
For Each timeZone As TimeZoneInfo In timeZones
Dim adjustments() As TimeZoneInfo.AdjustmentRule = timeZone.GetAdjustmentRules()
' Display message for time zones with no adjustments
If adjustments.Length = 0 Then
Console.WriteLine("{0} has no adjustment rules", timeZone.StandardName)
Else
' Handle time zones with 1 or 2+ adjustments differently
Dim showCount As Boolean = False
Dim ctr As Integer = 0
Dim spacer As String = ""
Console.WriteLine("{0} Adjustment rules", timeZone.StandardName)
If adjustments.Length > 1 Then showCount = True : spacer = " "
' Iterate adjustment rules
For Each adjustment As TimeZoneInfo.AdjustmentRule in adjustments
If showCount Then
Console.WriteLine(" Adjustment rule #{0}", ctr+1)
ctr += 1
End If
' 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
Dim transitionStart As TimeZoneInfo.TransitionTime = adjustment.DaylightTransitionStart
Console.Write("{0} Annual Start: ", spacer)
If transitionStart.IsFixedDateRule Then
Console.WriteLine("On {0} {1} at {2:t}", _
MonthName(transitionStart.Month), _
transitionStart.Day, _
transitionStart.TimeOfDay)
Else
Console.WriteLine("The {0} {1} of {2} at {3:t}", _
CType(transitionStart.Week, WeekOfMonth).ToString(), _
transitionStart.DayOfWeek.ToString(), _
MonthName(transitionStart.Month), _
transitionStart.TimeOfDay)
End If
' Get transition end information
Dim transitionEnd As TimeZoneInfo.TransitionTime = adjustment.DaylightTransitionEnd
Console.Write("{0} Annual End: ", spacer)
If transitionEnd.IsFixedDateRule Then
Console.WriteLine("On {0} {1} at {2:t}", _
MonthName(transitionEnd.Month), _
transitionEnd.Day, _
transitionEnd.TimeOfDay)
Else
Console.WriteLine("The {0} {1} of {2} at {3:t}", _
CType(transitionEnd.Week, WeekOfMonth).ToString(), _
transitionEnd.DayOfWeek.ToString(), _
MonthName(transitionEnd.Month), _
transitionEnd.TimeOfDay)
End If
Next
End If
Console.WriteLine()
Next
End Sub
Remarks
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 multiple adjustment rules, they are generally ordered from earliest (at index 0) to latest (at index Length - 1).
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.
Applies to
See also
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