TimeZoneInfo.IsAmbiguousTime Method

Definition

Namespace:

System

Assembly:

System.Runtime.dll

Determines whether a particular date and time in a particular time zone is ambiguous and can be mapped to two or more Coordinated Universal Time (UTC) times.

Overloads

IsAmbiguousTime(DateTime)	Determines whether a particular date and time in a particular time zone is ambiguous and can be mapped to two or more Coordinated Universal Time (UTC) times.
IsAmbiguousTime(DateTimeOffset)	Determines whether a particular date and time in a particular time zone is ambiguous and can be mapped to two or more Coordinated Universal Time (UTC) times.

IsAmbiguousTime(DateTime)

Source:

TimeZoneInfo.cs

Determines whether a particular date and time in a particular time zone is ambiguous and can be mapped to two or more Coordinated Universal Time (UTC) times.

public:
 bool IsAmbiguousTime(DateTime dateTime);

public bool IsAmbiguousTime (DateTime dateTime);

member this.IsAmbiguousTime : DateTime -> bool

Public Function IsAmbiguousTime (dateTime As DateTime) As Boolean

Parameters

dateTime

DateTime

A date and time value.

Returns

Boolean

true if the dateTime parameter is ambiguous; otherwise, false.

Exceptions

ArgumentException

The Kind property of the dateTime value is Local and dateTime is an invalid time.

Examples

In the Pacific Time zone, daylight saving time ends at 2:00 A.M. on November 4, 2007. The following example passes the time at one-minute intervals from 12:59 A.M. on November 4, 2007, to 2:01 A.M. on November 4, 2007, to the IsAmbiguousTime(DateTime) method of a TimeZoneInfo object that represents the Pacific Time zone. The console output indicates that all times from 1:00 A.M. on November 4, 2007, to 1:59 A.M. on November 4, 2007, are ambiguous.

   // Specify DateTimeKind in Date constructor
   DateTime baseTime = new DateTime(2007, 11, 4, 0, 59, 00, DateTimeKind.Unspecified);
   DateTime newTime;

   // Get Pacific Standard Time zone
   TimeZoneInfo pstZone = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time");

   // List possible ambiguous times for 63-minute interval, from 12:59 AM to 2:01 AM 
   for (int ctr = 0; ctr < 63; ctr++)
   {
      // Because of assignment, newTime.Kind is also DateTimeKind.Unspecified
      newTime = baseTime.AddMinutes(ctr);   
      Console.WriteLine("{0} is ambiguous: {1}", newTime, pstZone.IsAmbiguousTime(newTime));
   }

// Specify DateTimeKind in Date constructor
let baseTime = DateTime(2007, 11, 4, 0, 59, 00, DateTimeKind.Unspecified)

// Get Pacific Standard Time zone
let pstZone = TimeZoneInfo.FindSystemTimeZoneById "Pacific Standard Time"

// List possible ambiguous times for 63-minute interval, from 12:59 AM to 2:01 AM 
for i = 0 to 62 do
// Because of assignment, newTime.Kind is also DateTimeKind.Unspecified
    let newTime = baseTime.AddMinutes i   
    printfn $"{newTime} is ambiguous: {pstZone.IsAmbiguousTime newTime}"

' Specify DateTimeKind in Date constructor
Dim baseTime As New Date(2007, 11, 4, 0, 59, 00, DateTimeKind.Unspecified)
Dim newTime As Date

' Get Pacific Standard Time zone
Dim pstZone As TimeZoneInfo = TimeZoneInfo.FindSystemTimeZoneById("Pacific Standard Time")

' List possible ambiguous times for 63-minute interval, from 12:59 AM to 2:01 AM 
For ctr As Integer = 0 To 62
   ' Because of assignment, newTime.Kind is also DateTimeKind.Unspecified
   newTime = baseTime.AddMinutes(ctr)   
   Console.WriteLine("{0} is ambiguous: {1}", newTime, pstZone.IsAmbiguousTime(newTime))
Next

Remarks

An ambiguous time falls within a range of times for the current time zone. This means it can be either a standard time or a time that results from the application of an adjustment rule. Typically, ambiguous times result when the clock is set to return to standard time from daylight saving time. See the Example section for an illustration.

Coordinated Universal Time (UTC) has no ambiguous times; neither do time zones that do not support daylight saving time. Therefore, these time zones have no adjustment rules and calls to the IsAmbiguousTime method always return false.

For time zones that do observe daylight saving time, the precise behavior of this method depends on the relationship between the Kind property and the TimeZoneInfo object, as the following table shows.

TimeZoneInfo object type	Kind property value	Behavior
TimeZoneInfo.Local	DateTimeKind.Local or DateTimeKind.Unspecified	Determines whether the dateTime parameter is ambiguous.
TimeZoneInfo.Local	DateTimeKind.Utc	Converts dateTime to the local time and then determines whether that time is ambiguous.
TimeZoneInfo.Utc	DateTimeKind.Utc or DateTimeKind.Unspecified	Returns false.
TimeZoneInfo.Utc	DateTimeKind.Local	If dateTime is ambiguous, assumes it is a standard time, converts it to UTC, and returns false.
Any other time zone.	DateTimeKind.Local or DateTimeKind.Utc	Converts dateTime to the time in the specified time zone and then determines whether that time is ambiguous.
Any other time zone.	DateTimeKind.Unspecified	Determines whether dateTime is ambiguous.

See also

• IsInvalidTime(DateTime)

IsAmbiguousTime(DateTimeOffset)

Source:

TimeZoneInfo.cs

Determines whether a particular date and time in a particular time zone is ambiguous and can be mapped to two or more Coordinated Universal Time (UTC) times.

public:
 bool IsAmbiguousTime(DateTimeOffset dateTimeOffset);

public bool IsAmbiguousTime (DateTimeOffset dateTimeOffset);

member this.IsAmbiguousTime : DateTimeOffset -> bool

Public Function IsAmbiguousTime (dateTimeOffset As DateTimeOffset) As Boolean

Parameters

dateTimeOffset

DateTimeOffset

A date and time.

Returns

Boolean

true if the dateTimeOffset parameter is ambiguous in the current time zone; otherwise, false.

Remarks

An ambiguous time falls within a range of times for the current time zone. This means that it can be either a standard time or a time that results from the application of an adjustment rule. Typically, ambiguous times result when the clock is set to return to standard time from daylight saving time. Coordinated Universal Time (UTC) has no ambiguous times; neither do time zones that do not support daylight saving time.

The precise behavior of the method depends on the relationship between the Offset property of the dateTimeOffset parameter and the current time zone. If the value of the Offset property is a possible offset from the UTC of the current time zone, the method determines whether that date and time is ambiguous. Otherwise, it converts dateTimeOffset to the time in the current time zone, and then determines whether that date and time is ambiguous.