NET has a good set of date manipulation function, the various time zone conversion routines are a bit of a pain to use. I find myself having to look up what functions need to be called and review my thinking about how to best manage dates frequently. I see others struggling with this often as well, so I decided to take some time to write it down here in a post so I can find this info in one place. Web apps typically require that dates are stored in time zone agnostic fashion. This means storing DateTime values as UTC, so that you have a consistent baseline date value. This means storing dates in UTC format either with generated values using DateTime.UtcNowor, if you are capturing user input dates converting the time zone specific dates to UTC dates using. However in Web apps, this is not quite so easy because you can’t just use the server’s local time and use. ToUniversalTime() on a captured date input because that time reflects the server’s time, not necessarily the user’s time. So in addition to converting to UTC you also need to be able to convert user local dates to and from specific time zones which you can do with TimeZoneInfo.ConvertTime() and THEN convert that value to UTC. On the other end when retrieving dates you convert all dates from UTC dates to local dates according to the user’s time zone for which you need to using the TimeZoneInfo class.
You need two static methods from it: TimeZoneInfo.FindSystemTimeZoneById() and TimeZoneInfo.ConvertTimeFromUtc(). Also useful are TimeZoneInfo.ConvertTime()which converts between two timezones and TimeZoneInfo.ConvertTimeToUtc().
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