inject UTC time into the page - c#

I'm using several literals to inject the user's time onto the the page. The values in the HTML are the UTC times.
var TheDay = parseInt($('#UserDayToday').html(), 10);
var TheMonth = parseInt($('#UserMonthToday').html(), 10);
var TheYear = parseInt($('#UserYearToday').html(), 10);
var TheHours = parseInt($('#UserTimeStampHours').html(), 10);
var TheMinutes = parseInt($('#UserTimeStampMinutes').html(), 10);
Now I want to build a time stamp with that time so I tried this:
var TheDateToday = new Date();
TheDateToday.setUTCFullYear(TheYear, TheMonth, TheDay);
TheDateToday.setUTCHours(TheHours, TheMinutes, 0, 0);
alert(TheDateToday);
When the alert comes on, it gives me the time with his timezone shift added. How can I just have the the UTC time. I know I can get it from the browser but I want to get the UTC time built from the data sent from the server, not retrieved from the user's machine by the browser.
Thanks

You are displaying the date in local time. Use the toUTCString method instead of the implicit toString method:
alert(TheDateToday.toUTCString());

Related

convert date time to client time zone taking care of dst

i have date in pst format in database and i am passing it from backend via C# to javascript and then trying to convert it to client local time and here is the code i am using to convert it
onverttDate: function (element,date)
{
var Element = $(element);
var d1 = new Date(date);
var newDate = new Date(d1.getTime() + d1.getTimezoneOffset() * 60 * 1000);
var offset = d1.getTimezoneOffset() / 60;
var hours = d1.getHours();
newDate.setHours(hours offset);
Element.append('<div>' + newDate + '</div>');
}
and the date string i am getting from backend to javascript function is May 24,2014 09:59:59 and the converted date should be May 24,2014 22:59:59
i am not able to spot bug,i tried using moment.js also but its also not working.
Please give me a solution for this as what i am doing wrong.
Any, js fiddle example hardcoding date string as it is will also be appreciated
Note:I am getting date string from ajax call from server

Strange behavior from DateTime objects

I do the following:
var now = DateTime.Now;
var utc = DateTime.UtcNow;
var timeSpan = now - utc;
Console.WriteLine("Now is: " + now.ToString("yyyy-MM-dd HH:mm:ss:ms") + " utc is: " + utc.ToString("yyyy-MM-dd HH:mm:ss:ms") + " timeSpan: " +
timeSpan.TotalMinutes);
Console.ReadKey();
It gives the following result:
And if I take the timespan.hours (which is the one I actually use) it revelas 1?
Should be 2 What am I doing wrong there?
There is some time passes between you get times (system can even switch processes between these two calls):
var now = DateTime.Now;
// some time passes here
var utc = DateTime.UtcNow;
Thats why you have less than 2 hours between two values. You should get time only once and then convert it to local time:
var utc = DateTime.UtcNow;
var now = utc.ToLocalTime();
// timeSpan: 120
Or use TimeZoneInfo.ToUniversalTime to convert local time to UTC time:
var now = DateTime.Now;
var utc = TimeZone.CurrentTimeZone.ToUniversalTime(now);
The reason is simple: your calculation introduces an error by taking the time twice. The final result is slightly wrong, but the time taken to make the calls.
The solution is simpler.
Console.WriteLine(TimeZoneInfo.Local.BaseUtcOffset.Hours);
Console.WriteLine(TimeZoneInfo.Local.GetUtcOffset(DateTime.Now).Hours);
There is no need to get or convert times when what you actually want is time zone info. The first line gets the "normal" local time offset; the second gets the offset for 'now' in case your timezone is subject to daylight saving or other adjustments.

Convert UTC to local time with daylight saving on rdlc report

I pick up data which includes some date columns. Date returned from database is in UTC format. I feed this data to report viewer and want to show the date in local format, considering daylight saving.
I can do that from server side but I want the conversion to be according to the client machine timezone.
Is there any way to do it ?
Is your client a web page or a .NET app? If it is a .NET app you could do it like this. Firstly send your client timezone to your server like so:
string clientTimeZone = TimeZoneInfo.Local.ToSerializedString();
Then on your server:
var clientTimeZoneInfo = TimeZoneInfo.FromSerializedString(clientTimeZone);
var localDateTime = TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, clientTimeZoneInfo);
If this is a webapp use this javascript to send the offset to the server:
var timeNow = new Date();
var timezone = timeNow.getTimezoneOffset() / 60 * (-1);
Then on your server:
string clientTimeZoneOffset = "8";
var clientTimeZoneInfo = TimeZoneInfo.CreateCustomTimeZone("client", new TimeSpan(0, Int32.Parse(clientTimeZoneOffset), 0, 0),
"client", "client");
var utcDateTime = DateTime.UtcNow;
DateTime localDateTime = TimeZoneInfo.ConvertTimeFromUtc(utcDateTime, clientTimeZoneInfo);

How to convert a time and olson timezone to the time in another olson timezone?

I have as an input:
The time (8:00AM)
An Olson Timezone (America/New_York)
and I need to convert the time into another Olson Timezone (America/Los_Angeles)
What is the best way in .net or nodatime to do that conversion. I am basically looking for the equivalent of this method in C#:
var timeInDestinationTimeZone = TimeZoneInfo.ConvertTimeBySystemTimeZoneId(CurrentSlot.Date, TimeZoneInfo.Local.Id,
room.Location.TimeZone.TimeZoneName);
but this .Net method above only works with Windows Timezone names (and i have Olson names)
Observe:
var tzdb = DateTimeZoneProviders.Tzdb;
var zone1 = tzdb["America/New_York"];
var ldt1 = new LocalDateTime(2013, 3, 4, 8, 0); // March 4th, 2013 - 8:00 AM
var zdt1 = zone1.AtLeniently(ldt1);
var zone2 = tzdb["America/Los_Angeles"];
var zdt2 = zdt1.ToInstant().InZone(zone2);
var ldt2 = zdt2.LocalDateTime;
Notice the call to AtLeniently - that's because you don't have enough information to be absolutely certain of the moment in time you are talking about. For example, if you were talking about 1:30 AM on the day of a DST fall-back transition, you wouldn't know if you were talking about before or after the transition. AtLeniently will make the assumption you meant after. If you don't want that behavior, you have to provide an offset so you know which local time you were talking about.
The actual conversion is being done by ToInstant which is getting the UTC moment you're talking about, and then InZone which is applying it to the target zone.
An alternative to the second part of Matt's (perfectly good) answer:
// All of this part as before...
var tzdb = DateTimeZoneProviders.Tzdb;
var zone1 = tzdb["America/New_York"];
var ldt1 = new LocalDateTime(2013, 3, 4, 8, 0); // March 4th, 2013 - 8:00 AM
var zdt1 = zone1.AtLeniently(ldt1);
var zone2 = tzdb["America/Los_Angeles"];
// This is just slightly simpler - using WithZone, which automatically retains
// the calendar of the existing ZonedDateTime, and avoids having to convert
// to Instant manually
var zdt2 = zdt1.WithZone(zone2);
var ldt2 = zdt2.LocalDateTime;

How to get current user timezone in c#

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?
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.
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
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"];
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.
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();
}
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];
}
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
Take a look at this asp.net c# solution
TimeZoneInfo mytzone = TimeZoneInfo.Local;
System.Web.HttpContext.Current.Request.ServerVariables["HTTP_X_TIMEZONE"] ;

Categories

Resources