Does the .Net DateTime contain information about time zone where it was created?
I have a library parsing DateTime from a format that has "+zz" at the end, and while it parses correctly and adjusts a local time, I need to get what the specific time zone was from the DateTime object.
Is this possible at all? All I can see is DateTime.Kind, which specifies if time is local or UTC.
DateTime itself contains no real timezone information. It may know if it's UTC or local, but not what local really means.
DateTimeOffset is somewhat better - that's basically a UTC time and an offset. However, that's still not really enough to determine the timezone, as many different timezones can have the same offset at any one point in time. This sounds like it may be good enough for you though, as all you've got to work with when parsing the date/time is the offset.
The support for time zones as of .NET 3.5 is a lot better than it was, but I'd really like to see a standard "ZonedDateTime" or something like that - a UTC time and an actual time zone. It's easy to build your own, but it would be nice to see it in the standard libraries.
EDIT: Nearly four years later, I'd now suggest using Noda Time which has a rather richer set of date/time types. I'm biased though, as the main author of Noda Time :)
No.
A developer is responsible for keeping track of time-zone information associated with a DateTime value via some external mechanism.
A quote from an excellent article here.
A must read for every .Net developer.
So my advice is to write a little wrapper class that suits your needs.
There is a public domain TimeZone library for .NET. Really useful. It will answer your needs.
Solving the general-case timezone problem is harder than you think.
You could use TimeZoneInfo class
The TimeZone class recognizes local time zone, and can convert times between Coordinated Universal Time (UTC) and local time. A TimeZoneInfo object can represent any time zone, and methods of the TimeZoneInfo class can be used to convert the time in one time zone to the corresponding time in any other time zone. The members of the TimeZoneInfo class support the following operations:
Retrieving a time zone that is already defined by the operating
system.
Enumerating the time zones that are available on a system.
Converting times between different time zones.
Creating a new time zone that is not already defined by the
operating system.
Serializing a time zone for later retrieval.
From the API (http://msdn.microsoft.com/en-us/library/system.datetime_members(VS.71).aspx) it does not seem it can show the name of the time zone used.
DateTime does not know its timezone offset. There is no built-in method to return the offset or the timezone name (e.g. EAT, CEST, EST etc).
Like suggested by others, you can convert your date to UTC:
DateTime localtime = new DateTime.Now;
var utctime = localtime.ToUniversalTime();
and then only calculate the difference:
TimeSpan difference = localtime - utctime;
Also you may convert one time to another by using the DateTimeOffset:
DateTimeOffset targetTime = DateTimeOffset.Now.ToOffset(new TimeSpan(5, 30, 0));
But this is sort of lossy compression - the offset alone cannot tell you which time zone it is as two different countries may be in different time zones and have the same time only for part of the year (eg. South Africa and Europe). Also, be aware that summer daylight saving time may be introduced at different dates (EST vs CET - a 3-week difference).
You can get the name of your local system time zone using TimeZoneInfo class:
TimeZoneInfo localZone = TimeZoneInfo.Local;
localZone.IsDaylightSavingTime(localtime) ? localZone.DaylightName : localZone.StandardName
I agree with Gerrie Schenck, please read the article he suggested.
Generally the practice would be to pass data as a DateTime with a "timezone" of UTC and then pass a TimeZoneInfo object and when you are ready to display the data, you use the TimeZoneInfo object to convert the UTC DateTime.
The other option is to set the DateTime with the current timezone, and then make sure the "timezone" is unknown for the DateTime object, then make sure the DateTime is again passed with a TimeZoneInfo that indicates the TimeZone of the DateTime passed.
As others have indicated here, it would be nice if Microsoft got on top of this and created one nice object to do it all, but for now you have to deal with two objects.
Related
I am trying to change TimeOnly value to local TimeOnly.
What is the best way to do this in .NET? There isn't built in method to do this.
Thank you.
Because of daylight savings, local time has no meaning unless you also know the date. You need a date as part of the value or you can't really know what time to use for a given local timezone.
C# supports different timezone id's across the globe. Please find list of time zones that are being supported by C# in below link:
https://msdn.microsoft.com/en-us/library/gg154758.aspx
The timezone id's are used in C# library functions to convert times across the timezones.
[e.g. TimeZoneInfo.ConvertTimeBySystemTimeZoneId("Hawaiian Standard Time")]
Similarly I want support for AMERICA/MIQUELON, which is not present in the msdn list provided in above link.
Can somebody please provide workaround for this specific timezone?
Time zone identifiers like "America/Miquelon" and the others you listed (before editing your question) are from the IANA time zone database. You can read more in the timezone tag wiki and on Wikipedia.
Note that they are usually presented in mixed case form, rather than in all capital letters.
The easiest and best way to work with these in .NET is via the Noda Time library.
For example:
DateTimeZone tz = DateTimeZoneProviders.Tzdb["America/Miquelon"];
Instant now = SystemClock.Instance.Now;
ZonedDateTime converted = now.InZone(tz);
What is the idiomatic way to get the system's time as a LocalDateTime in Noda Time? The most direct method I could think of would be
var dt = DateTime.Now
LocalDateTime systemTime = new LocalDateTime(dt.Year, dt.Month, dt.Day, dt.Hour, dt.Minute);
but given that Noda Time's entire purpose is to replace DateTime with something that has nicer semantics, I assumed there was a preferred method than to use DateTime in the above manner. The best I could come up with using Noda's facilities is
var zone = NodaTime.TimeZones.BclDateTimeZone.ForSystemDefault();
LocalDateTime systemTime = SystemClock.Instance.Now.InZone(zone).LocalDateTime;
but this seems quite verbose.
Your second example is exactly how you would do this. It is intentionally verbose. See Noda Time's design philosophy.
Think of it in three parts:
Get the current moment in time:
// Instant now = SystemClock.Instance.Now; // NodaTime 1.x
Instant now = SystemClock.Instance.GetCurrentInstant(); // NodaTime 2.x
Get the system's time zone. (This is the preferred syntax)
DateTimeZone tz = DateTimeZoneProviders.Bcl.GetSystemDefault();
Apply the time zone to the instant:
ZonedDateTime zdt = now.InZone(tz);
Your last step of getting a LocalDateTime is trivial, but recognize that when you do it, you are stripping away any time zone information. "Local" in NodaTime does not mean "local to the computer where the code is running". (In other words, it's not like DateTimeKind.Local)
Additional things to think about:
You may prefer to abstract the clock using the IClock interface:
IClock clock = SystemClock.Instance;
// Instant now = clock.Now; // NodaTime 1.x
Instant now = clock.GetCurrentInstant(); // NodaTime 2.x
Then you could pass the clock in as a method parameter, or inject it with your favorite DI/IoC framework. (Autofac, Ninject, StructureMap, whatever...). The advantage is then you could use a NodaTime.Testing.FakeClock during your unit tests. See Unit Testing with Noda Time for more details.
You might also prefer to pass in the DateTimeZone so you can run your code anywhere without being tied to the system time zone. This is important for server applications, but less so for desktop/mobile apps.
If you have other work that's using IANA time zones, or if you're using the .NET Standard build of Noda Time, then change step 2 to use the Tzdb provider:
DateTimeZone tz = DateTimeZoneProviders.Tzdb.GetSystemDefault();
The TZDB zones are much more accurate than the BCL zones. Noda Time will map your system's Windows (BCL) time zone to an IANA (TZDB) time zone in this initial call.
If you have curiosity into why DateTime.Now is so compact while Noda Time is so verbose, try decompiling DateTime.Now or looking at the MS reference sources. You'll see that it's doing essentially the same steps under the hood.
I have the following list of time zones that a user can choose from, Mountain Standard Time is in there twice for Arizona. These aren't want they see when they choose. I pulled this list of a website that had all of Microsofts time zones. I guess I'm confused if it had Mountain Standard Time listed for the regular states and AZ.
Hawaiian Standard Time
Alaskan Standard Time
Pacific Standard Time
Mountain Standard Time
Mountain Standard Time
Central Standard Time
Central America Standard Time
Eastern Standard Time
U.S. Eastern Standard Time
My question is I'm guessing these don't account for DST, so I'm assuming I need to add something to my conversion to check and see if they're in DST and adjust it accordingly. Here is how I'm doing the conversion now.
TimeZoneInfo time = TimeZoneInfo.FindSystemTimeZoneById(LocationProvider.GetLocation(LocationID).TimeZone.Name);
return TimeZoneInfo.ConvertTime(DateTime.Now, time);
Yes, TimeZoneInfo accounts for DST, so long as you use it properly (which isn't as easy as it might be, admittedly). It's not really clear why you're trying to do what you're doing though...
I know it's confusing that the ID is actually the standard ID for the time zone, but it's still a full time zone that knows about DST. It doesn't just mean "standard time".
(If you get frustrated with DateTime et al and fancy trying Noda Time for all your date/time needs, I'd be happy to help out :)
I want to find out what will be the time in india when clock tick to 1Am mid night in any other country..
How i will find out that through any means
plz help me to find out this
this is to fire birthbay mails at 1AM midnight of that resp country...
.NET 3.5 added the class TimeZoneInfo which should be able to do want you want. Particularly, the TimeZoneInfo.ConvertTime(DateTime, TimeZoneInfo, TimeZoneInfo) method.
You can also use the TimeZoneInfo.GetSystemTimeZones() method to get the list of time zones that are registered in the system.
You might want to look at the method:
TimeZoneInfo.ConvertTime
SQL SERVER 2008 would have the DATETIMEOFFSET data type (which includes the time zone) plus functions like SWITCHOFFSET to switch from one timezone offset to another.
What version are you on?