I answered a question over at StackOverflow, and I really liked the answer, so I thought I would share this nifty extension method:
/// <summary>
/// Convert a given DateTime object to a user's local time,
/// taking into account changes in TimeZone rules.
/// For example, if you were to perform this operation on
/// a time now, during EST Daylight Saving, and that time falls
/// outside the scope of Daylight Saving time, the rule will adjust accordingly.
/// </summary>
/// <param name="dateTime">The DateTime object</param>
/// <param name="offset">offset from UTC</param>
/// <returns>User's local time</returns>
public static DateTime ConvertToLocalDateTime(this DateTime dateTime, int offset)
{
TimeZoneInfo destinationTimeZone = TimeZoneInfo.GetSystemTimeZones()
.Where(x => x.BaseUtcOffset.Hours.Equals(offset)).FirstOrDefault();
var rule = destinationTimeZone.GetAdjustmentRules().Where(x =>
x.DateStart <= dateTime && dateTime <= x.DateEnd)
.FirstOrDefault();
TimeSpan baseOffset = TimeSpan.Zero;
if (rule != null)
{
baseOffset -= destinationTimeZone.IsDaylightSavingTime(dateTime) ?
rule.DaylightDelta : TimeSpan.Zero;
}
DateTimeOffset dto = DateTimeOffset.Parse(dateTime.ToString());
return new DateTime(TimeZoneInfo
.ConvertTimeFromUtc(dateTime,
destinationTimeZone).Ticks + baseOffset.Ticks);
}
The summary basically says it all. I ran through a couple of tests with this, I’d like to know if anyone uses this and makes modifications to it!