Jon's answer talks about TimeZone, but I'd suggest using TimeZoneInfo instead.
Personally I like keeping things in UTC where possible (at least for the past; storing UTC for the future has potential issues), so I'd suggest a structure like this:
public struct DateTimeWithZone
{
private readonly DateTime utcDateTime;
private readonly TimeZoneInfo timeZone;
public DateTimeWithZone(DateTime dateTime, TimeZoneInfo timeZone)
{
var dateTimeUnspec = DateTime.SpecifyKind(dateTime, DateTimeKind.Unspecified);
utcDateTime = TimeZoneInfo.ConvertTimeToUtc(dateTimeUnspec, timeZone);
this.timeZone = timeZone;
}
public DateTime UniversalTime { get { return utcDateTime; } }
public TimeZoneInfo TimeZone { get { return timeZone; } }
public DateTime LocalTime
{
get
{
return TimeZoneInfo.ConvertTime(utcDateTime, timeZone);
}
}
}
You may wish to change the "TimeZone" names to "TimeZoneInfo" to make things clearer - I prefer the briefer names myself.