Correct approach to getting the universal time zone

Question

In my project I want to get the universal time zone. I used two different kinds of approaches but I don't know which one is the best practice.

First approach is

public static DateTime GetUniversalTime(DateTime localDateTime)
{
    TimeZone zone = TimeZone.CurrentTimeZone;
    DateTime universal = zone.ToUniversalTime(localDateTime);
    return universal;
}

then I want revert to local time I used the below method:

public static DateTime GetLocalTime(DateTime universalDateTime)
{
    TimeZone zone = TimeZone.CurrentTimeZone;
    DateTime local = zone.ToLocalTime(universalDateTime);
    return local;
}

and second approach is get universal time zone DateTime.UtcNow; then I want to revert to local time I used the above GetLocalTime method.

Can one explain what is the different between the above two approaches?

Which one is the best practice ?

I'm not sure, but I think there might be different ways to do the same thing. So those might be equivalent solutions, just one is a shortcut. — Sasha, Apr 04 '14 at 12:54
@OleksandrPshenychnyy thanks... Have any shortcut for get local time ? — Niventh, Apr 04 '14 at 12:56
dateTime.ToLocalTime() is much shorter than your previous solution and gives same result I believe — Sasha, Apr 04 '14 at 13:01
@CodingKiwi when you need to get current time, then yes. But when you have time stored in DB, then it is different task — Sasha, Apr 04 '14 at 13:04
@CodingKiwi No, I stored the universal time in to database. i need to convert in to local time whenever time showing UI — Niventh, Apr 04 '14 at 13:05
Ah I see. This answer gives a different approach, although I'm not sure if it counts as neater: http://stackoverflow.com/a/963812/128386 — Fiona - myaccessible.website, Apr 04 '14 at 13:07

score 2 · Accepted Answer · edited May 23 '17 at 10:24

Since you are asking about best practices:

Do not use the TimeZone class. If you need time zone conversions, use the TimeZoneInfo class instead. This is very clear in the MSDN documentation:
Whenever possible, avoid any use of "local" time. It is local to the system where the code is running. In the vast majority of real-world use cases, it is likely that it is not the local time zone of your user. This is especially true in a web application.

That means you should not be calling any of the following:
- DateTime.Now
- TimeZone.CurrentTimeZone
- TimeZoneInfo.Local
- DateTime.ToLocalTime()
- DateTime.ToUniversalTime()
- Any other method that involves the server's local time zone.
Instead, your application should allow the user to select a time zone, then you can convert to and from the local time in that zone using the TimeZoneInfo.Convert... methods.
If you need the current universal time, use DateTime.UtcNow or DateTimeOffset.UtcNow.
If you need the current local time zone of your server, ONLY use DateTimeOffset.Now.

If you need the current local time in a known time zone, such as US Eastern Time:

DateTime easternNow = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(
                                   DateTime.UtcNow, "Eastern Standard Time");

If you want to convert between a known time zone and UTC, then use the TimeZoneInfo.ConvertTimeToUtc and TimeZoneInfo.ConvertTimeFromUtc methods, and be sure to pass in the time zone you are converting to/from:

// get the local time zone of your user, not of the server!
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("Eastern Standard Time");

// use this to convert from UTC to local
DateTime local = TimeZoneInfo.ConvertTimeFromUtc(yourUtcDateTime, tzi);

// use this to convert from local to UTC
DateTime utc = TimeZoneInfo.ConvertTimeToUtc(yourLocalDateTime, tzi);

Be aware that when you convert from local to UTC, you might encounter ambiguities during daylight saving time transitions. Read more in the DST tag wiki.

Additional reading: The Case Against DateTime.Now

score -3 · Answer 2 · answered Apr 04 '14 at 12:50

-3

For Universal Time.

DateTime.Now.ToUniversalTime()

For Local Time

DateTime.UtcNow.ToLocalTime()

Universal To Local

var nowUtc = DateTime.Now.ToUniversalTime();
var nowLocal = nowUtc.ToLocalTime();

answered Apr 04 '14 at 12:50

halit

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the question is not about that. This is one of his own solutions – Sasha Apr 04 '14 at 12:52
I don't want new approaches. The above method is working fine but i want know whats is the different between TimeZone and DateTime.UtcNow; – Niventh Apr 04 '14 at 12:53
Both of them same. Because Timezone Knows hour difference Local and Universal. When your LocalTime is UTC +3 . TouniversalTime extension will subtract 3 hour from local. If you send Universal Time as paramater to GetUniversalTime funtion IT'll return equal result with parameter. Becase DataTime object stores TimezoneInfo . Same Logic for ToLocalTime. – halit Apr 04 '14 at 13:06

Correct approach to getting the universal time zone

2 Answers2