How to get current user timezone in c#

Question

I am building an application in MVC3 and when a user comes into my site I want to know that user's timezone. I want to know how to do this in c# not in javaScript?

Sokil

Related post : #338982 – Fusillade

testing to see what timestamp SO puts... posted at 3:54pm EST – Picklock

Answer 1

As has been mentioned, you need your client to tell your ASP.Net server details about which timezone they're in.

Here's an example.

I have an Angular controller, which loads a list of records from my SQL Server database in JSON format. The problem is, the DateTime values in these records are in the UTC timezone, and I want to show the user the date/times in their local timezone.

I determine the user's timezone (in minutes) using the JavaScript "getTimezoneOffset()" function, then append this value to the URL of the JSON service I'm trying to call:

$scope.loadSomeDatabaseRecords = function () {

    var d = new Date()
    var timezoneOffset = d.getTimezoneOffset();

    return $http({
        url: '/JSON/LoadSomeJSONRecords.aspx?timezoneOffset=' + timezoneOffset,
        method: 'GET',
        async: true,
        cache: false,
        headers: { 'Accept': 'application/json', 'Pragma': 'no-cache' }
    }).success(function (data) {
        $scope.listScheduleLog = data.Results;
    });
}

In my ASP.Net code, I extract the timezoneOffset parameter...

int timezoneOffset = 0;

string timezoneStr = Request["timezoneOffset"];
if (!string.IsNullOrEmpty(timezoneStr))
    int.TryParse(timezoneStr, out timezoneOffset);

LoadDatabaseRecords(timezoneOffset);

... and pass it to my function which loads the records from the database.

It's a bit messy as I want to call my C# FromUTCData function on each record from the database, but LINQ to SQL can't combine raw SQL with C# functions.

The solution is to read in the records first, then iterate through them, applying the timezone offset to the DateTime fields in each record.

public var LoadDatabaseRecords(int timezoneOffset)
{
    MyDatabaseDataContext dc = new MyDatabaseDataContext();

    List<MyDatabaseRecords> ListOfRecords = dc.MyDatabaseRecords.ToList();

    var results = (from OneRecord in ListOfRecords
           select new
           {
               ID = OneRecord.Log_ID,
               Message = OneRecord.Log_Message,
               StartTime =  FromUTCData(OneRecord.Log_Start_Time, timezoneOffset),
               EndTime = FromUTCData(OneRecord.Log_End_Time, timezoneOffset)
           }).ToList();

    return results;
}

public static DateTime? FromUTCData(DateTime? dt, int timezoneOffset)
{
    //  Convert a DateTime (which might be null) from UTC timezone
    //  into the user's timezone. 
    if (dt == null)
        return null;

    DateTime newDate = dt.Value - new TimeSpan(timezoneOffset / 60, timezoneOffset % 60, 0);
    return newDate;
}

It works nicely though, and this code is really useful when writing a web service to display date/times to users in different parts of the world.

Right now, I'm writing this article at 11am Zurich time, but if you were reading it in Los Angeles, you'd see that I edited it at 2am (your local time). Using code like this, you can get your webpages to show date times that make sense to international users of your website.

Phew.

Hope this helps.

Zwart

Thank you Mike. I realized you can do new TimeSpan(0, timezoneOffset, 0) and it calculates the number of hours properly. – Shore

DST shouldn't matter. Your JavaScript will take this into account when you call "getTimezoneOffset()". All that matters is that, on the server, DateTimes are always UTC-based, and on the client, we're correctly passing the timezone offset. – Zwart

Regarding DST, it does matter, but only if you are doing something like storing it. For time zones that observe DST, the offset will be different in daylight vs standard time. So the offset will be correct when you get it, but not if you keep it around for a while. – Dyke

This gives you the current offset from UTC, not the time zone. See "Time Zone != Offset" in the timezone tag wiki. – Disorder

Great answer, but in reality you shouldn't be doing this. You should retreive the data as-is (in UTC) and have Angular apply the offsetting. – Merryman

Answer 2

This isn't possible server side unless you assume it via the users ip address or get the user to set it in some form of a profile. You could get the clients time via javascript.

See here for the javacript solution: Getting the client's timezone in JavaScript

Coburn

Answer 3

You will need to use both client-side and server-side technologies.

On the client side:
(pick one)

• This works in most modern browsers:

  Intl.DateTimeFormat().resolvedOptions().timeZone
  

• There is also jsTimeZoneDetect's jstz.determine(), or Moment-Timezone's moment.tz.guess() function for older browsers, thought these libraries are generally only used in older applications.

The result from either will be an IANA time zone identifier, such as America/New_York. Send that result to the server by any means you like.

On the server side:
(pick one)

• Using TimeZoneInfo (on. NET 6+ on any OS, or older on non-Windows systems only):

  TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById("America/New_York");
  

• Using TimeZoneConverter (on any OS):

  TimeZoneInfo tzi = TZConvert.GetTimeZoneInfo("America/New_York");
  

• Using NodaTime (on any OS):

  DateTimeZone tz = DateTimeZoneProviders.Tzdb["America/New_York"];
  

Disorder

Answer 4

I got the same issue , Unfortunately there is no way for the server to know the client timezone . If you want you can send client timezone as header while making ajax call .

In-case if you want more info on adding the header this post may help how to add header to request : How can I add a custom HTTP header to ajax request with js or jQuery?

new Date().getTimezoneOffset();//gets the timezone offset

If you don't want to add header every time , you can think of setting a cookie since cookie is sent with all httpRequest you can process the cookie to get client timezone on server side . But i don't prefer adding cookies , for the same reason they sent with all http requests. Thanks.

Petit

Putting the timezone in a cookie is a great alternative for when you don't want to use ajax requests for this, plus you don't have to use JavaScript to display a date, only to set the cookie. – Pungent

@RuudLenders but you need javascript to set the cookie once – Siskind

This gives you the current offset from UTC, not the time zone. See "Time Zone != Offset" in the timezone tag wiki. – Disorder

@MattJohnson: I know that, But this is as close as we can get. Mostly we use timezone info for manipulating datetime, where we need only offset, not really timezone. Can you give me a different better solution for finding that? – Petit

Yes, see my answer to this question. – Disorder

Answer 5

For Dot Net version 3.5 and higher you can use :

TimeZoneInfo.Local.GetUtcOffset(DateTime.UtcNow);

but for Dot Net lower than version 3.5 you can handle it manually via this way :

first, get Offset from the client and store it in the cookie

function setTimezoneCookie(){
 
var timezone_cookie = "timezoneoffset";

// if the timezone cookie does not exist create one.
if (!$.cookie(timezone_cookie)) { 

    // check if the browser supports cookie
    var test_cookie = 'test cookie';
    $.cookie(test_cookie, true);

    // browser supports cookie
    if ($.cookie(test_cookie)) { 
     
        // delete the test cookie
        $.cookie(test_cookie, null);
     
        // create a new cookie 
        $.cookie(timezone_cookie, new Date().getTimezoneOffset());

        // re-load the page
        location.reload(); 
    }
}
// if the current timezone and the one stored in cookie are different
// then store the new timezone in the cookie and refresh the page.
else {         

    var storedOffset = parseInt($.cookie(timezone_cookie));
    var currentOffset = new Date().getTimezoneOffset();

    // user may have changed the timezone
    if (storedOffset !== currentOffset) { 
        $.cookie(timezone_cookie, new Date().getTimezoneOffset());
        location.reload();
    }
}

}

after that you can use a cookie in backend code like that :

   public static string ToClientTime(this DateTime dt)
{
    // read the value from session
    var timeOffSet = HttpContext.Current.Session["timezoneoffset"];  
 
    if (timeOffSet != null) 
    {
        var offset = int.Parse(timeOffSet.ToString());
        dt = dt.AddMinutes(-1 * offset);
 
        return dt.ToString();
    }
 
    // if there is no offset in session return the datetime in server timezone
    return dt.ToLocalTime().ToString();
}

Divinity

The JQuery javascript works only with jquery-cookie installed. – Afield

Please note that TimeZoneOffset is not the same as TimeZone. Knowing the clients timezone, arbitrary (past and future) DateTime's can be converted to other TimeZones, honoring DST transitions etc., whereas TimeZomeOffset only has a meaning for converting DateTime.Now. Replacing new Date().getTimezoneOffset() with Intl.DateTimeFormat().resolvedOptions().timeZone will give the TimeZone. – Afield

Answer 6

I know the user asked about a non-javascript solution, but I wanted to post a javascript solution that I came up with. I found some js libraries (jsTimezoneDetect, momentjs), but their output was an IANA code, which didn't seem to help me with getting a TimeZoneInfo object in C#. I borrowed ideas from jsTimezoneDetect. In javascript, I get the BaseUtcOffset and the first day of DST and send to server. The server then converts this to a TimeZoneInfo object.

Right now I don't care if the client Time Zone is chosen as "Pacific Time (US)" or "Baja California" for example, as either will create the correct time conversions (I think). If I find multiple matches, I currently just pick the first found TimeZoneInfo match.

I can then convert my UTC dates from the database to local time:

DateTime clientDate = TimeZoneInfo.ConvertTimeFromUtc(utcDate, timeZoneInfo);

Javascript

// Time zone.  Sets two form values:
// tzBaseUtcOffset: minutes from UTC (non-DST)
// tzDstDayOffset: number of days from 1/1/2016 until first day of DST ; 0 = no DST
var form = document.forms[0];
var janOffset = -new Date(2016, 0, 1).getTimezoneOffset();      // Jan
var julOffset = -new Date(2016, 6, 1).getTimezoneOffset();      // Jul
var baseUtcOffset = Math.min(janOffset, julOffset);             // non DST offset (winter offset)
form.elements["tzBaseUtcOffset"].value = baseUtcOffset;
// Find first day of DST (from 1/1/2016)
var dstDayOffset = 0;
if (janOffset != julOffset) {
    var startDay = janOffset > baseUtcOffset ? 180 : 0; // if southern hemisphere, start 180 days into year
    for (var day = startDay; day < 365; day++) if (-new Date(2016, 0, day + 1, 12).getTimezoneOffset() > baseUtcOffset) { dstDayOffset = day; break; }    // noon
}
form.elements["tzDstDayOffset"].value = dstDayOffset;

C#

    private TimeZoneInfo GetTimeZoneInfo(int baseUtcOffset, int dstDayOffset) {

        // Converts client/browser data to TimeZoneInfo
        // baseUtcOffset: minutes from UTC (non-DST)
        // dstDayOffset: number of days from 1/1/2016 until first day of DST ; 0 = no DST
        // Returns first zone info that matches input, or server zone if none found

        List<TimeZoneInfo> zoneInfoArray = new List<TimeZoneInfo>();    // hold multiple matches
        TimeSpan timeSpan = new TimeSpan(baseUtcOffset / 60, baseUtcOffset % 60, 0);
        bool supportsDst = dstDayOffset != 0;
        foreach (TimeZoneInfo zoneInfo in TimeZoneInfo.GetSystemTimeZones()) {
            if (zoneInfo.BaseUtcOffset.Equals(timeSpan) && zoneInfo.SupportsDaylightSavingTime == supportsDst) {
                if (!supportsDst) zoneInfoArray.Add(zoneInfo);
                else {
                    // Has DST. Find first day of DST and test for match with sent value. Day = day offset into year
                    int foundDay = 0;
                    DateTime janDate = new DateTime(2016, 1, 1, 12, 0, 0);  // noon
                    int startDay = zoneInfo.IsDaylightSavingTime(janDate) ? 180 : 0;    // if southern hemsphere, start 180 days into year
                    for (int day = startDay; day < 365; day++) if (zoneInfo.IsDaylightSavingTime(janDate.AddDays(day))) { foundDay = day; break; }
                    if (foundDay == dstDayOffset) zoneInfoArray.Add(zoneInfo);
                }
            }
        }
        if (zoneInfoArray.Count == 0) return TimeZoneInfo.Local;
        else return zoneInfoArray[0];
    }

Pages

Answer 7

You can get this information from client to server (any web API call)

var timezoneOffset = new Date().getTimezoneOffset();

With the help of timezoneoffset details you can achieve the same. Here in my case i converted UTC DateTime to my client local datetime in Server side.

DateTime clientDateTime = DateTime.UtcNow - new TimeSpan(timezoneOffset / 60, timezoneOffset % 60, 0);

Click for code example

Jacalynjacamar

Answer 8

Take a look at this asp.net c# solution

TimeZoneInfo mytzone = TimeZoneInfo.Local;

Hausa

This is local to the server, not the user. – Tipperary

This is the solution I needed for a local client application (non-web). [+] – Jordanson

Answer 9

System.Web.HttpContext.Current.Request.ServerVariables["HTTP_X_TIMEZONE"] ;

Tris

Could you provide a reference to this information? A code snippet without any context is not very valuable. – Apodaca

As above, useless answer. – Noncommittal