In .NET, the following statements return different values:
Response.Write( TimeZoneInfo.ConvertTime( DateTime.Parse("2010-07-01 5:30:00.000"),
Here is a discussion of Coordinated Univeral Timezones. It seems that UTC is usually used when a high precision is need for the time frame. Greenwhich Meantime is pretty close and is used back and forth with UTC.
Hope this helps some.