.NET TimeZoneInfo wrong about Daylight savings

Question

Can anyone help make sense of this. Microsoft’s TimeZoneInfo class in 3.5 is telling me the following GMT date is not in Daylight savings for the Eastern timezone, but it i

Answer 1

This will work:

TimeZoneInfo tzEasternZone = TimeZoneInfo.FindSystemTimeZoneById(
                                          "Eastern Standard Time");

DateTime utc = DateTime.Parse("2009-11-01T05:00:00Z",
                              CultureInfo.InvariantCulture,
                              DateTimeStyles.RoundtripKind);

bool isDaylight = tzEasternZone.IsDaylightSavingTime(utc);

The original code had two issues:

• Even though a UTC value was being provided, it was getting converted to local kind in the Parse statement. So ambiguity could be introduced there.

• The IsDaylightTime method on the DateTime class will assume the local time zone if the kind is local or unspecified. After calling ConvertTime, the result has unspecified kind, so it was checking against the rules of the local time zone, not the eastern time zone.