无法完成转换，因为提供的 DateTime 没有正确设置 Kind 属性

Question

I am trying convert UK time into UTC in C#

DateTime utc = DateTime.UtcNow;
var ukTimeZone = TimeZoneInfo.FindSystemTimeZoneById("GMT Standard Time");
DateTime ukTime = TimeZoneInfo.ConvertTime(utc,ukTimeZone, TimeZoneInfo.Local );

Console.WriteLine(ukTime);

But I got this error.

Unhandled exception. System.ArgumentException: The conversion could not be completed because the supplied DateTime did not have the Kind property set correctly. For example, when the Kind property is DateTimeKind.Local, the source time zone must be TimeZoneInfo.Local. (Parameter 'sourceTimeZone') at System.TimeZoneInfo.ConvertTime(DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone, TimeZoneInfoOptions flags, CachedData cachedData) at System.TimeZoneInfo.ConvertTime(DateTime dateTime, TimeZoneInfo sourceTimeZone, TimeZoneInfo destinationTimeZone)

But if I run the below code

DateTime time = new DateTime(2022, 11, 09, 23, 47, 00);
var ukTimeZone = TimeZoneInfo.FindSystemTimeZoneById("GMT Standard Time");
DateTime ukTime = TimeZoneInfo.ConvertTime(time,ukTimeZone, TimeZoneInfo.Local );
Console.WriteLine(ukTime);

I got the expected result: 11/09/2022 23:47:00

Why does this error occur? What is the difference between time and utc ?

Answer 1

The DateTimeKind associated with a DateTime is determined by how you construct it:

DateTime.UtcNow.Kind == DateTimeKind.Utc
DateTime.Now.Kind == DateTimeKind.Local
new DateTime(2022, 11, 9, 23, 47, 0) == DateTimeKind.Unspecified

The docs for the TimeZoneInfo.ConvertTime method you are calling describes the behavior you are observing:

Exceptions

ArgumentException

The Kind property of the dateTime parameter is Local , but the sourceTimeZone parameter does not equal Local .

-or-

The Kind property of the dateTime parameter is Utc , but the sourceTimeZone parameter does not equal Utc .

-or-

The dateTime parameter is an invalid time (that is, it represents a time that does not exist because of a time zone's adjustment rules).

Your first example demonstrates the second reason described for the exception. That is:

• The Kind property of the input value is DateTimeKind.Utc
• The source time zone you are passing is "GMT Standard Time" , not "UTC"

These time zones are not the same.

• "GMT Standard Time" corresponds to "(UTC+00:00) Dublin, Edinburgh, Lisbon, London"
• "UTC" corresponds to "(UTC) Coordinated Universal Time"

The primary difference being that London uses UTC+1 during the summer months when British Summer Time (a daylight saving time) is in effect. Reference: https://www.timeanddate.com/time/zone/uk/london

Conversely, UTC is not necessarily the time in the UK. It's a time standard that applies universally to the entire planet. It never observes daylight saving time.