Capture UTC Time From String And Format All DateTime To It

Question

I have a date that is being returned in a string format

string utcdt = "2017-01-01T15:48:00-07:00";

How could I extract the 07:00 Mountain Time from the string above and format any date to this regional formatting?

I do not want to change timezones on my computer, as the UTC time returned to the variable utcdt can vary depending, and all other dates used in my WinForm app would need to conform to the same timezone specifications.

Edit
I am using the FEDEx API and this is one format of the date returnerd

string utcdt = "2017-01-01T15:48:00-07:00";

Now later in the application there is

foreach (TrackingDateOrTimestamp timestamp in trackDetail.DatesOrTimes)
    Console.WriteLine("{0}: {1}", timestamp.Type, timestamp.DateOrTimestamp);

Which returns the data in my local time - meaning

01/01/2017 17:48:00

I am trying to come up with a solution to have the dates be consistent.

Answer 1

You can use the DateTimeOffset class to parse the string into the local time and it's offset from UTC. You can then save the offset as a TimeSpan .

Later on then again use the DateTimeOffset class to convert another DateTime you have to use the same offset:

string dto = "2017-01-01T15:48:00-07:00";

DateTimeOffset dateTimeOffset = DateTimeOffset.Parse(dto);

DateTime utcDateTime = dateTimeOffset.UtcDateTime;
TimeSpan timezoneOffset = dateTimeOffset.Offset;


MessageBox.Show("UTC DateTime: " + utcDateTime);
MessageBox.Show("Offset: " + timezoneOffset);

DateTimeOffset nowWithOffset = DateTimeOffset.UtcNow.ToOffset(timezoneOffset);

MessageBox.Show("Now in other timezone: " + nowWithOffset.ToString("O"));

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Note what other commentators have written: This does not correctly deal with Daylight Saving Time. In order to deal with that, you actually need to know the real timezone.