From what I have researched it is not possible to change the Timezone of a thread. So my question is why can't you?
I would have thought switching your application's culture to a specific country would also switch this, seems like expected behaviour IMO.
Edit
After revising I can see the reason why it probably shouldn't be mapped 1:1 by default. However, I still feel it would be a nice feature to be able to change the Timezone per thread.
They aren't a 1:1 so they're not really connected. If you set the current culture to en-US, which timezone is that? :)
Several countries have more than 1 timezone, so setting the culture (which is not country specific either for that matter), doesn't really have much to do with the timzone.
Culture is one thing, time zone is another. Suppose you're a South African citizen working in New York, USA. Obviously you want your time zone to be EST (GMT -5), since that's where you are; from what you're suggesting, however, then if you also set your culture to "af-ZA," as you might want to, doing so would automatically change your time zone to GMT +2.
Related
I'm building a system where you got a lot of places, all around the world that need to show if they're open or close in real time.
The thing I've been debating on is how to do it, having never build this in any other project, I don't really know what is the best idea to achieve this goal.
I'd like to do it the right way so that I don't have to rebuild the entire date and time system later.
I use C# and .NET 5.0 for the API and Xamarin.Forms for the mobile app.
What I was thinking was:
Either I use regular DateTime for the times and input, let's say, oh this place closes at 11pm, doesn't matter if it's in Sweden or UK, basically their Time Zone doesn't matter. Compare the place's closing time to the user's phone's internal region and time and if the user's phone says it's 11pm and the place closes at 11pm, display it as closed on their phone. I don't think it's a good idea because I think this data should be changed at the API level, not run a method for each user running the app, but I might be wrong.
Or, I actually create times related to their Time Zones such as, I don't know what to use yet to be honest but, say DateTimeOffset or something and actually add the TimeZone as a property to the place's Address, then in the API compare it to the place's current time in its region and mark it as open or close for everyone in the world since it's on the server.
It might be a very simple question but I want to make sure I'm doing this right.
I'm building a system where you got a lot of places, all around the
world that need to show if they're open or close in real time.
That's great.
The thing I've been debating on is how to do it, having never build
this in any other project, I don't really know what is the best idea
to achieve this goal. I'd like to do it the right way so that I don't
have to rebuild the entire date and time system later.
Exactly, you don't need to reinvent the wheel. There a lot of example on the internet that you can use for that. Just be careful to create your system design based on your requirements.
Either I use regular DateTime for the times and input, let's say, oh
this place closes at 11pm, doesn't matter if it's in Sweden or UK,
basically their Time Zone doesn't matter. Compare the place's closing
time to the user's phone's internal region and time and if the user's
phone says it's 11pm and the place closes at 11pm, display it as
closed on their phone. I don't think it's a good idea because I think
this data should be changed at the API level, not run a method for
each user running the app, but I might be wrong.
Yes, that's not a great idea. Nowadays, actually smart phones are quite smart to update their local time when they have internet connection but "region" subject is still under users control. That's why the subject of "local time" will be always depends on user regions, phones time zone system and how up to date of "that" system. For example, you can still live in Turkey but you "can" set your region settings for another country, like Germany. In that case, "the place where user lives" and "region settings on the phone" matters. My 11:00PM can be easily different than your 11:00PM.
One of the solutions can be taking location information on the phone and calculating user's time zone and inform and/or compare phone's time.
A nice guy named Matt Johnson-Pint created 2 useful library for that. GeoTimeZone and TimeZoneConverter. You can find the time zone information of the user for longitude and latitude easily.
For example;
string tzIana = TimeZoneLookup.GetTimeZone(lat, lng).Result;
TimeZoneInfo tzInfo = TZConvert.GetTimeZoneInfo(tzIana);
DateTimeOffset convertedTime = TimeZoneInfo.ConvertTime(DateTimeOffset.UtcNow, tzInfo);
Remember, time zones matters!
Or, I actually create times related to their Time Zones such as, I
don't know what to use yet to be honest but, say DateTimeOffset or
something and actually add the TimeZone as a property to the place's
Address, then in the API compare it to the place's current time in its
region and mark it as open or close for everyone in the world since
it's on the server.
Yes, that sounds more logical.
Please let me know how I should do it and also explain how I should
implement it in detail
Sorry, Stack Overflow is for specific programming problems and this part of your question does not meet the standart of asking a proper question. Please read Help Center a few times before asking more questions.
I am storing all the DateTime fields as UTC time. When a user requests a web page, I would like to take his preferred local timezone (and not the local timezone of the server machine) and automatically display all the DateTime fields in all the web forms as local dates.
Of course, I could apply the conversion on every DateTime.ToString() call in every form or implement some helper utility but it is a time consuming task, and also there are some 3rd party components which are tricky to configure with custom DateTime display templates.
Essentially, I would like to make the DateTime class to behave as follows:
from this moment on for this web request,
whenever some code calls DateTime.ToString(), convert it to the local time
using the timezone offset given at the very beginning of the web request,
but if possible, please keep .NET core library DateTime.ToString() calls intact
(I don't want to mess up event logging timestamps etc.)
Is there any way to do it?
BTW, I am using ASP.NET MVC 4, if it matters.
You can't do directly what you asked for, but I will suggest some alternatives. As Nicholas pointed out, there is nothing in HTTP that would give you the time zone directly.
Option 1
First, decide which type of time zone data you want to work with. There are two different types available, either the Microsoft time zones that you can access with the TimeZoneInfo class, or the IANA/Olson time zones that the rest of the world uses. Read here for more info. My recommendation would be the latter, using the implementation provided by NodaTime.
Then determine which time zone you want to convert to. You should allow your user a setting somewhere to pick their time zone.
You might show a drop-down list to pick one of several time zones, or you might do something more useful, like display a map of the world that they can click to select their time zone. There are several libraries that can do this in Javascript, but my favorite is this one.
You might want to guess a default time zone to use, so you can be as close to accurate as possible before they pick from the list (or map). There is a great library for this called jsTimeZoneDetect. It will interrogate the browser's clock and make a best guess assumption of what time zone it might be. It is fairly good, but it is still just a guess. Don't use it blindly - but do use it to determine a starting point. Update You can now also do this with moment.tz.guess(), in the moment-timezone component of moment.js.
Now that you know the time zone of the user, you can use that value to convert your UTC DateTime values to that local time zone. Unfortunately, there is nothing you can set on the thread that will do that. When you change the system time zone, it is global for all processes and threads. So you have no choice but to pass the time zone to each and every place you are sending it back. (I believe this was your main question.) See this almost duplicate here.
Before you convert it to a string, you will need to also know the user's locale (which you can get from the Request.UserLanguages value). You can assign it to the current thread, or you can pass it as a parameter to the DateTime.ToString() method. This doesn't do any time zone conversion - it just makes sure that the numbers are in the correct position, using the correct separators, and the appropriate language for names of weekdays or months.
Option 2
Don't convert it to local time on the server at all.
Since you said you are working with UTC values, make sure their .Kind property is Utc. You should probably do this when you load from your database, but if you have to you can do it manually:
myDateTime = DateTime.SpecifyKind(myDateTime, DateTimeKind.Utc);
Send it back to the browser as pure UTC, in an invariant format like ISO8601. In other words:
myDateTime.ToString("o"); // example: "2013-05-02T21:01:26.0828604Z"
Use some JavaScript on the browser to parse it as UTC. It will automatically pick up the local time settings of the browser. One way is to use the built-in Date object in JavaScript, like this:
var dt = new Date('2013-05-02T21:01:26.0828604Z');
However, this will only work in newer browsers that support the ISO-8601 format. Instead, I recommend using the moment.js library. It is consistent across browsers, and it has better support for ISO dates, and localization. Plus you get a lot of other useful parsing and formatting functions.
// pass the value from your server
var m = moment('2013-05-02T21:01:26.0828604Z');
// use one of the formats supported by moment.js
// this is locale-specific "long date time" format.
var s = m.format('LLLL');
The advantage of Option 1 is that you can work with times in any time zone. If you can ask the user for their timezone from a dropdown list, then you need not use any Javascript.
The advantage of Option 2 is that you get the browser to do some of the work for you. This is the best way to go if you're sending out raw data, such as making AJAX calls to a WebAPI. However, JavaScript is only aware of UTC and the browser's local time zone. So it doesn't work so well if you need to convert to other zones.
You should also be aware that if you choose Option #2, you may be affected by a flaw in the design of ECMAScript 5.1. This comes into play if you are working with dates that are covered by a different set of daylight saving time rules than are currently in effect. You can read more in this question, and on my blog.
It would be so much easier if we had some time zone information in the HTTP headers, but unfortunately we don't. These are a lot of hoops to jump through, but it's the best way to have both flexibility and accuracy.
The short answer is that you can't. HTTP doesn't require (or even provide a standard way) for the user agent (browser) to provide local time or timezone information in the HTTP request.
You either need to
ask the user for their preferred time zone, or
have client-side javascript report it to you somehow (cookie? ajax? other?)
Bear in mind that a client-side javascript solution isn't perfect, either. Javascript disabled (or non-existent, for some browsers). Javascript might not have access to timezone information. Etc.
I need to know the timezone for a certain language which I get from the current culture info object.
I can not use 3rd party libs like nodatime.
What property of the CultureInfo.CurrentCulture is important when I enumerate through all system time zones and want to get the right timezone?
If all you've got is culture, that's basically some string like: MX (Spanish Mexico), es-CO (Spanish Columbia), and fr-CA (French Canada) then you just have to correspond each on of these to a timezone, except no such one to one relationship exists. So no. You can roughly know the timezone (as pointed out in comments), fr-CA is all in the same timezone, but MX is in four (MX isn't enough information to gauge timezone).
So you don't have enough data to know, what can you do. If you need to know their timezone on the server side try geo-location:
How can I find a user's GEO Location using ASP.NET?
However, if it's just the web page that needs to know, try putting that logic in the JavaScript which is executing on their machine.
Or you could just... ask them.
I am using .Net 4.0. I am working on an application which was first meant for USA only but now its getting global. Issue is:
All calculations done in USA or other country happens to be in their individual time zone. Now when we want to compare or filter some data based on a particular date then they dont match as time part of the whole date is different. I know we cant implement application wide timezone like a Culture thing. But is there a way to make minimal code changes and compare only Date part of the DateTime properties in the whole application.
Date which was saved in USA timezone comes as below when India user checks them:
23-Oct-2014 09:30:00 AM
Now when a India user wants to filter 23-Oct-2014 data, nothing is returned because:
23-Oct-2014 09:30:00 AM is not equal to 23-Oct-2014 12:00:00 AM
I dont want to make change in thousands for DateTime properties in whole application, Is there a way to correct the issue with minimal code change for whole application. Any help is greatly appreciated.
This may sound crazy, and I don't know if this will work with all of your code. Especially if you have 3rd party libraries
but if you add a structure to the project under the System namespace
and name it DateTime then it will override the real System.DateTime and it's use will have the swiggly underlines with a message saying it conflicts with the original and is using yours.
I don't think this is a great idea but if you copy the datetime code and change what you need
it just might work.
DateTime.cs
I am storing all the DateTime fields as UTC time. When a user requests a web page, I would like to take his preferred local timezone (and not the local timezone of the server machine) and automatically display all the DateTime fields in all the web forms as local dates.
Of course, I could apply the conversion on every DateTime.ToString() call in every form or implement some helper utility but it is a time consuming task, and also there are some 3rd party components which are tricky to configure with custom DateTime display templates.
Essentially, I would like to make the DateTime class to behave as follows:
from this moment on for this web request,
whenever some code calls DateTime.ToString(), convert it to the local time
using the timezone offset given at the very beginning of the web request,
but if possible, please keep .NET core library DateTime.ToString() calls intact
(I don't want to mess up event logging timestamps etc.)
Is there any way to do it?
BTW, I am using ASP.NET MVC 4, if it matters.
You can't do directly what you asked for, but I will suggest some alternatives. As Nicholas pointed out, there is nothing in HTTP that would give you the time zone directly.
Option 1
First, decide which type of time zone data you want to work with. There are two different types available, either the Microsoft time zones that you can access with the TimeZoneInfo class, or the IANA/Olson time zones that the rest of the world uses. Read here for more info. My recommendation would be the latter, using the implementation provided by NodaTime.
Then determine which time zone you want to convert to. You should allow your user a setting somewhere to pick their time zone.
You might show a drop-down list to pick one of several time zones, or you might do something more useful, like display a map of the world that they can click to select their time zone. There are several libraries that can do this in Javascript, but my favorite is this one.
You might want to guess a default time zone to use, so you can be as close to accurate as possible before they pick from the list (or map). There is a great library for this called jsTimeZoneDetect. It will interrogate the browser's clock and make a best guess assumption of what time zone it might be. It is fairly good, but it is still just a guess. Don't use it blindly - but do use it to determine a starting point. Update You can now also do this with moment.tz.guess(), in the moment-timezone component of moment.js.
Now that you know the time zone of the user, you can use that value to convert your UTC DateTime values to that local time zone. Unfortunately, there is nothing you can set on the thread that will do that. When you change the system time zone, it is global for all processes and threads. So you have no choice but to pass the time zone to each and every place you are sending it back. (I believe this was your main question.) See this almost duplicate here.
Before you convert it to a string, you will need to also know the user's locale (which you can get from the Request.UserLanguages value). You can assign it to the current thread, or you can pass it as a parameter to the DateTime.ToString() method. This doesn't do any time zone conversion - it just makes sure that the numbers are in the correct position, using the correct separators, and the appropriate language for names of weekdays or months.
Option 2
Don't convert it to local time on the server at all.
Since you said you are working with UTC values, make sure their .Kind property is Utc. You should probably do this when you load from your database, but if you have to you can do it manually:
myDateTime = DateTime.SpecifyKind(myDateTime, DateTimeKind.Utc);
Send it back to the browser as pure UTC, in an invariant format like ISO8601. In other words:
myDateTime.ToString("o"); // example: "2013-05-02T21:01:26.0828604Z"
Use some JavaScript on the browser to parse it as UTC. It will automatically pick up the local time settings of the browser. One way is to use the built-in Date object in JavaScript, like this:
var dt = new Date('2013-05-02T21:01:26.0828604Z');
However, this will only work in newer browsers that support the ISO-8601 format. Instead, I recommend using the moment.js library. It is consistent across browsers, and it has better support for ISO dates, and localization. Plus you get a lot of other useful parsing and formatting functions.
// pass the value from your server
var m = moment('2013-05-02T21:01:26.0828604Z');
// use one of the formats supported by moment.js
// this is locale-specific "long date time" format.
var s = m.format('LLLL');
The advantage of Option 1 is that you can work with times in any time zone. If you can ask the user for their timezone from a dropdown list, then you need not use any Javascript.
The advantage of Option 2 is that you get the browser to do some of the work for you. This is the best way to go if you're sending out raw data, such as making AJAX calls to a WebAPI. However, JavaScript is only aware of UTC and the browser's local time zone. So it doesn't work so well if you need to convert to other zones.
You should also be aware that if you choose Option #2, you may be affected by a flaw in the design of ECMAScript 5.1. This comes into play if you are working with dates that are covered by a different set of daylight saving time rules than are currently in effect. You can read more in this question, and on my blog.
It would be so much easier if we had some time zone information in the HTTP headers, but unfortunately we don't. These are a lot of hoops to jump through, but it's the best way to have both flexibility and accuracy.
The short answer is that you can't. HTTP doesn't require (or even provide a standard way) for the user agent (browser) to provide local time or timezone information in the HTTP request.
You either need to
ask the user for their preferred time zone, or
have client-side javascript report it to you somehow (cookie? ajax? other?)
Bear in mind that a client-side javascript solution isn't perfect, either. Javascript disabled (or non-existent, for some browsers). Javascript might not have access to timezone information. Etc.