Linq to SQL DateTime values are local (Kind=Unspecified) - How do I make it UTC?

Question

Isn\'t there a (simple) way to tell Linq To SQL classes that a particular DateTime property should be considered as UTC (i.e. having the Kind property of the DateTime type t

Answer 1

SQL Server DateTime does not include any timezone or DateTimeKind information, therefore DateTime values retrieved from the database correctly have Kind = DateTimeKind.Unspecified.

If you want to make these times UTC, you should 'convert' them as follows:

DateTime utcDateTime = new DateTime(databaseDateTime.Ticks, DateTimeKind.Utc);

or the equivalent:

DateTime utcDateTime = DateTime.SpecifyKind(databaseDateTime, DateTimeKind.Utc);

I assume your problem is that you are attempting to convert them as follows:

DateTime utcDateTime = databaseDateTime.ToUniversalTime();

This may appear reasonable at first glance, but according to the MSDN documentation for DateTime.ToUniversalTime, when converting a DateTime whose Kind is Unspecified:

The current DateTime object is assumed to be a local time, and the conversion is performed as if Kind were Local.

This behavior is necessary for backwards compatibility with .NET 1.x, which didn't have a DateTime.Kind property.