Converting DateTime to UTC and back

Question

Maybe it will sound a bit weird, but i actually know a solution for this problem. My initial solution didn't work and i actually want to why. It is an Asp.Net MVC application.

This didn't work:

        public static DateTime ConvertToUTC(String userTimeZone, DateTime date)
    {
        var result = TimeZoneInfo.ConvertTimeToUtc(date, TimeZoneInfo.FindSystemTimeZoneById(userTimeZone));

        return result;
    }

    public static DateTime ConvertToUserTime(string userTimeZone, DateTime date)
    {
        var result = TimeZoneInfo.ConvertTimeFromUtc(date, TimeZoneInfo.FindSystemTimeZoneById(userTimeZone));

        return result;
    }

I couldn't convert the time back to it's original time.

This did work:

public DateTime ConvertToUTC(String userTimeZone, DateTime date)
    {

        var result = TimeZoneInfo.ConvertTimeToUtc(result, TimeZoneInfo.FindSystemTimeZoneById(userTimeZone));

        return result;
    }

    public DateTime ConvertToUserTime(string userTimeZone, DateTime date)
    {
        var userTimezoneInfo = TimeZoneInfo.FindSystemTimeZoneById(userTimeZone);
        var result = date.Add(userTimezoneInfo.BaseUtcOffset);

        return result;
    }

Does anybody have an idea?

Answer 1

对于此问题，.NET 3.5中引入了特殊的DataType： DateTimeOffset，其功能与DateTime类似，但它还存储UTC偏移量。