Difference between UTC and GMT Standard Time in .NET

Question

In .NET, the following statements return different values:

Response.Write(
  TimeZoneInfo.ConvertTime(
    DateTime.Parse("2010-07-01 5:30:00.000"),         


        

Answer 1

GMT does not adjust for Daylight saving time (DST). You can hear it from the horse's mouth on this web site.

Add this line of code to see the source of the problem:

  Console.WriteLine(TimeZoneInfo.FindSystemTimeZoneById("GMT Standard Time").SupportsDaylightSavingTime);

Output: True.

This is not a .NET problem, it is Windows messing up. The registry key that TimeZoneInfo uses is HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones\GMT Standard Time. You'd better stick with UTC.