Convert same time to different time zone

Question

I am trying to convert times to different time zones, but not the way you're thinking. I need to convert a DateTime that is 9am EST to 9am CST on the UTC for example. The timezones are variable so just adding/subtracting hours doesn't seem correct way to do it with NodaTime

Fri, 21 Feb 2014 21:00:00 EST = 1393034400 Epoch Timestamp
convert to
Fri, 21 Feb 2014 21:00:00 CST = 1393030800 Epoch Timestamp

Answer 1

If I understand the question correctly, it sounds like you're trying to convert a date/time in one time zone to another one that has the same local time and a different time zone; that is, a different point in time.

You can do this with Noda Time by combining the LocalDateTime with the new zone. For example, given something like the following:

Instant now = SystemClock.Instance.Now;
DateTimeZone eastern = DateTimeZoneProviders.Tzdb["America/New_York"];
ZonedDateTime nowEastern = now.InZone(eastern);

nowEastern is the time now in the America/New_York time zone. If we print nowEastern directly to the console, we'll see something like 2014-02-22T05:18:50 America/New_York (-05).

As an aside, "EST" and "CST" aren't time zones: they're non-unique abbreviations for a particular offset within a time zone; America/New_York and America/Chicago are probably representative of what we think of as "Eastern" and "Central", though (or you could use something like UTC-05:00 if you really wanted EST even when daylight savings time was in effect).

Given a ZonedDateTime in any time zone, we can convert it to a ZonedDateTime with the same local time and a specified time zone as follows:

DateTimeZone central = DateTimeZoneProviders.Tzdb["America/Chicago"];
ZonedDateTime sameLocalTimeCentral = nowEastern.LocalDateTime.InZoneStrictly(central);

This gives us a ZonedDateTime with the same local time, but a different time zone. With the input above, the result would be 2014-02-22T05:18:50 America/Chicago (-06).

Note that I'm using InZoneStrictly. This will throw an exception if the local time is ambiguous or invalid (for example, during daylight savings transitions). If that's unacceptable, you could use InZoneLeniently, which picks the earliest valid ZonedDateTime on or after the given local time, or InZone, which allows you to specify your own rules in those cases.

Answer 2

On Msdn website you can find all you need.

Small example:

DateTime dateNow = DateTime.Now;
Console.WriteLine("The date and time are {0} UTC.", 
               TimeZoneInfo.ConvertTimeToUtc(dateNow));

Go to the link for more details on what you want, I can't give you more with that small description