Determine a user s timezone

Question

Is there a standard way for a web server to be able to determine a user s timezone within a web page    Perhaps from an HTTP header or part of the user-agent string

User · Answer

A simple way to do it is by using   new Date   getTimezoneOffset

User · Answer

Here is an article  with source code  that explains how to determine and use localized time in an ASP NET  VB NET  C   application    It s About Time  In short  the described approach relies on the JavaScript getTimezoneOffset function  which returns the value that is saved in the session cookie and used by code-behind to adjust time values between GMT and local time  The nice thing is that the user does not need to specify the time zone  the code does it automatically   There is more involved  this is why I link to the article   but provided code makes it really easy to use  I suspect that you can convert the logic to PHP and other languages  as long as you understand ASP NET

User · Answer

There s no such way to figure the timezone in the actual HTML code or any user-agent string  but what you can do is make a basic function getting it using JavaScript  I don t know how to code with JavaScript yet so my function might take time to make  However  you can try to get the actual timezone also using JavaScript with the getTzimezoneOffset   function in the Date section or simply new Date   getTimezoneOffset

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To submit the timezone offset as an HTTP header on AJAX requests with jQuery    ajaxSetup       beforeSend  function xhr  settings            xhr setRequestHeader  X-TZ-Offset   -new Date   getTimezoneOffset   60               You can also do something similar to get the actual time zone name by using moment tz guess    from http   momentjs com timezone docs   using-timezones guessing-user-timezone

User · Answer

With the PHP date function you will get the date time of server on which the site is located  The only way to get the user time is to use JavaScript   But I suggest you to  if your site has registration required then the best way is to ask the user while to have registration as a compulsory field  You can list various time zones in the register page and save that in the database  After this  if the user logs in to the site then you can set the default time zone for that session as per the users    selected time zone   You can set any specific time zone using the PHP function date default timezone set  This sets the specified time zone for users   Basically the users    time zone is goes to the client side  so we must use JavaScript for this   Below is the script to get users    time zone using PHP and JavaScript    lt  php      http   www php net manual en timezones php List of Time Zones     function showclienttime                 if  isset   COOKIE  GMT bias                 gt                lt script type  text javascript  gt                  var Cookies                       Cookies create   function  name  value  days                        if  days                            var date   new Date                            date setTime date getTime      days   24   60   60   1000                            var expires      expires     date toGMTString                                              else                           var expires                                                 document cookie   name         value   expires      path                         this name    value                                     var now   new Date                    Cookies create  GMT bias  now getTimezoneOffset   1                   window location     lt  php echo   SERVER  PHP SELF     gt                 lt  script gt                lt  php                    else              fct clientbias     COOKIE  GMT bias                        fct servertimedata   gettimeofday             fct servertime    fct servertimedata  sec             fct serverbias    fct servertimedata  minuteswest             fct totalbias    fct serverbias      fct clientbias           fct totalbias    fct totalbias   60           fct clienttimestamp    fct servertime    fct totalbias           fct time   time             fct year   strftime   Y    fct clienttimestamp            fct month   strftime   B    fct clienttimestamp            fct day   strftime   d    fct clienttimestamp            fct hour   strftime   I    fct clienttimestamp            fct minute   strftime   M    fct clienttimestamp            fct second   strftime   S    fct clienttimestamp            fct am pm   strftime   p    fct clienttimestamp           echo  fct day       fct month      fct year        fct hour      fct minute      fct second      fct am pm                  showclienttime      gt    But as per my point of view  it   s better to ask to the users if registration is mandatory in your project

User · Answer

All the magic seems to be in visitortime getTimezoneOffset    That s cool  I didn t know about that  Does it work in Internet Explorer etc  From there you should be able to use JavaScript to Ajax  set cookies whatever  I d probably go the cookie route myself  You ll need to allow the user to change it though  We tried to use geo-location  via maxmind  to do this a while ago  and it was wrong enough to make it not worth doing  So we just let the user set it in their profile  and show a notice to users who haven t set theirs yet

User · Answer

JavaScript is the easiest way to get the client s local time  I would suggest using an XMLHttpRequest to send back the local time  and if that fails  fall back to the timezone detected based on their IP address   As far as geolocation  I ve used MaxMind GeoIP on several projects and it works well  though I m not sure if they provide timezone data  It s a service you pay for and they provide monthly updates to your database  They provide wrappers in several web languages

User · Answer

It is simple with JavaScript and PHP   Even though the user can mess with his her internal clock and or timezone  the best way I found so far  to get the offset  remains new Date   getTimezoneOffset     It s non-invasive  doesn t give head-aches and eliminates the need to rely on third parties   Say I have a table  users  that contains a field date created int 13   for storing Unix timestamps   Assuming a client creates a new account  data is received by post  and I need to insert update the date created column with the client s Unix timestamp  not the server s   Since the timezoneOffset is needed at the time of insert update  it is passed as an extra   POST element when the client submits the form  thus eliminating the need to store it in sessions and or cookies  and no additional server hits either   var off    -new Date   getTimezoneOffset   60  toString     note the  -  in front which makes it return positive for negative offsets and negative for positive offsets var tzo   off     0     GMT    off indexOf  -    gt  -1    GMT  off    GMT   off    Say the server receives tzo as   POST  tzo      ts   new DateTime  now   new DateTimeZone   POST  tzo      user time    ts- gt format  F j  Y  g i a     will return the users current time in readable format  regardless of whether date default timezone   is set or not   user timestamp   strtotime  user time     Insert update date created  user timestamp   When retrieving the date created  you can convert the timestamp like so    date created      Get from the database  created   date  F j  Y  g i a   date created      Return it to the user or whatever   Now  this example may fit one s needs  when it comes to inserting a first timestamp    When it comes to an additional timestamp  or table  you may want to consider inserting the tzo value into the users table for future reference  or setting it as session or as a cookie   P S  BUT what if the user travels and switches timezones  Logs in at GMT 4  travels fast to GMT-1 and logs in again  Last login would be in the future   I think    we think too much

User · Answer

Don t use the IP address to definitively determine location  and hence timezone -- that s because with NAT  proxies  increasingly popular   and VPNs  IP addresses do not necessarily realistically reflect the user s actual location  but the location at which the servers implementing those protocols reside   Similar to how US area codes are no longer useful for locating a telephone user  given the popularity of number portability   IP address and other techniques shown above are useful for suggesting a default that the user can adjust correct

User · Answer

If you happen to be using OpenID for authentication  Simple Registration Extension would solve the problem for authenticated users  You ll need to convert from tz to numeric    Another option would be to infer the time zone from the user agent s country preference  This is a somewhat crude method  won t work for en-US   but makes a good approximation

User · Answer

Try this PHP code    lt  php      ip     SERVER  REMOTE ADDR         json   file get contents  http   api easyjquery com ips  ip      ip     amp full true         json   json decode  json true        timezone    json  LocalTimeZone      gt

User · Answer

You could do it on the client with moment-timezone and send the value to server  sample usage    gt  moment tz guess    America Asuncion

User · Answer

There are no HTTP headers that will report the clients timezone so far although it has been suggested to include it in the HTTP specification   If it was me  I would probably try to fetch the timezone using clientside JavaScript and then submit it to the server using Ajax or something

User · Answer

One possible option is to use the Date header field  which is defined in RFC 7231 and is supposed to include the timezone  Of course  it is not guaranteed that the value is really the client s timezone  but it can be a convenient starting point

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Here is a more complete way    Get the timezone offset for the user Test some days on daylight saving boundaries to determine if they are in a zone that uses daylight saving    An excerpt is below   function TimezoneDetect        var dtDate   new Date  1 1      new Date    getUTCFullYear         var intOffset   10000    set initial offset high so it is adjusted on the first attempt     var intMonth      var intHoursUtc      var intHours      var intDaysMultiplyBy          Go through each month to find the lowest offset to account for DST     for  intMonth 0 intMonth  lt  12 intMonth               go to the next month         dtDate setUTCMonth dtDate getUTCMonth     1               To ignore daylight saving time look for the lowest offset             Since  during DST  the clock moves forward  it ll be a bigger number          if  intOffset  gt   dtDate getTimezoneOffset      -1                 intOffset    dtDate getTimezoneOffset      -1                         return intOffset      Getting TZ and DST from JS  via Way Back Machine

User · Answer

Easy  just use the JavaScript getTimezoneOffset function like so   -new Date   getTimezoneOffset   60

User · Answer

First  understand that time zone detection in JavaScript is imperfect   You can get the local time zone offset for a particular date and time using getTimezoneOffset on an instance of the Date object  but that s not quite the same as a full IANA time zone like America Los Angeles  There are some options that can work though   Most modern browsers support IANA time zones in their implementation of the ECMAScript Internationalization API  so you can do this    x000D   x000D  const tzid   Intl DateTimeFormat   resolvedOptions   timeZone  console log tzid   x000D   x000D   x000D   The result is a string containing the IANA time zone setting of the computer where the code is running  Supported environments are listed in the Intl compatibility table  Expand the DateTimeFormat section  and look at the feature named resolvedOptions   timeZone defaults to the host environment   Some libraries  such as Luxon use this API to determine the time zone through functions like luxon Settings defaultZoneName   If you need to support an wider set of environments  such as older web browsers  you can use a library to make an educated guess at the time zone   They work by first trying the Intl API if it s available  and when it s not available  they interrogate the getTimezoneOffset function of the Date object  for several different points in time  using the results to choose an appropriate time zone from an internal data set  Both jsTimezoneDetect and moment-timezone have this functionality       using jsTimeZoneDetect   var tzid   jstz determine   name          using moment-timezone   var tzid   moment tz guess     In both cases  the result can only be thought of as a guess   The guess may be correct in many cases  but not all of them  Additionally  these libraries have to be periodically updated to counteract the fact that many older JavaScript implementations are only aware of the current daylight saving time rule for their local time zone   More details on that here    Ultimately  a better approach is to actually ask your user for their time zone   Provide a setting that they can change   You can use one of the above options to choose a default setting  but don t make it impossible to deviate from that in your app  There s also the entirely different approach of not relying on the time zone setting of the user s computer at all   Instead  if you can gather latitude and longitude coordinates  you can resolve those to a time zone using one of these methods   This works well on mobile devices

User · Answer

JavaScript   function maketimus timestampz        var linktime   new Date timestampz   1000       var linkday   linktime getDate        var freakingmonths   new Array         freakingmonths 0      jan       freakingmonths 1      feb       freakingmonths 2      mar       freakingmonths 3      apr       freakingmonths 4      may       freakingmonths 5      jun       freakingmonths 6      jul       freakingmonths 7      aug       freakingmonths 8      sep       freakingmonths 9      oct       freakingmonths 10     nov       freakingmonths 11     dec        var linkmonthnum   linktime getMonth        var linkmonth   freakingmonths linkmonthnum       var linkyear   linktime getFullYear        var linkhour   linktime getHours        var linkminute   linktime getMinutes         if  linkminute  lt  10                linkminute    0    linkminute             var fomratedtime   linkday   linkmonth   linkyear                                linkhour         linkminute    h       return fomratedtime      Simply provide your times in Unix timestamp format to this function  JavaScript already knows the timezone of the user   Like this   PHP   echo   lt script type  text javascript  gt  var eltimio   maketimus    unix timestamp ofshiz     document write eltimio    lt  script gt  lt noscript gt pls enable javascript lt  noscript gt      This will always show the times correctly based on the timezone the person has set on his her computer clock  There is no need to ask anything to anyone and save it into places  thank god

User · Answer

Here s how I do it  This will set the PHP default timezone to the user s local timezone  Just paste the following on the top of all your pages    lt  php session start     if  isset   SESSION  timezone           if  isset   REQUEST  offset                 gt           lt script gt          var d   new Date           var offset  -d getTimezoneOffset   60          location href     lt  php echo   SERVER  PHP SELF      gt  offset   offset           lt  script gt           lt  php              else                zonelist   array  Kwajalein    gt  -12 00   Pacific Midway    gt  -11 00   Pacific Honolulu    gt  -10 00   America Anchorage    gt  -9 00   America Los Angeles    gt  -8 00   America Denver    gt  -7 00   America Tegucigalpa    gt  -6 00   America New York    gt  -5 00   America Caracas    gt  -4 30   America Halifax    gt  -4 00   America St Johns    gt  -3 30   America Argentina Buenos Aires    gt  -3 00   America Sao Paulo    gt  -3 00   Atlantic South Georgia    gt  -2 00   Atlantic Azores    gt  -1 00   Europe Dublin    gt  0   Europe Belgrade    gt  1 00   Europe Minsk    gt  2 00   Asia Kuwait    gt  3 00   Asia Tehran    gt  3 30   Asia Muscat    gt  4 00   Asia Yekaterinburg    gt  5 00   Asia Kolkata    gt  5 30   Asia Katmandu    gt  5 45   Asia Dhaka    gt  6 00   Asia Rangoon    gt  6 30   Asia Krasnoyarsk    gt  7 00   Asia Brunei    gt  8 00   Asia Seoul    gt  9 00   Australia Darwin    gt  9 30   Australia Canberra    gt  10 00   Asia Magadan    gt  11 00   Pacific Fiji    gt  12 00   Pacific Tongatapu    gt  13 00            index   array keys  zonelist    REQUEST  offset               SESSION  timezone      index 0            date default timezone set   SESSION  timezone        rest of your code goes here   gt

User · Answer

Using Unkwntech s approach  I wrote a function using jQuery and PHP  This is tested and does work   On the PHP page where you want to have the timezone as a variable  have this snippet of code somewhere near the top of the page    lt  php     session start         timezone     SESSION  time      gt    This will read the session variable  time   which we are now about to create   On the same page  in the  lt head   you need to first of all include jQuery    lt script type  text javascript  src  http   code jquery com jquery-latest min js  gt  lt  script gt    Also in the  lt head   below the jQuery  paste this    lt script type  text javascript  gt        document  ready function             if   lt  php echo  timezone    gt   length  0               var visitortime   new Date                var visitortimezone    GMT     -visitortime getTimezoneOffset   60                ajax                   type   GET                   url   http   example org timezone php                   data   time    visitortimezone                  success  function                        location reload                                                         lt  script gt    You may or may not have noticed  but you need to change the URL to your actual domain   One last thing  You are probably wondering what the heck timezone php is  Well  it is simply this   create a new file called timezone php and point to it with the above URL    lt  php     session start          SESSION  time       GET  time      gt    If this works correctly  it will first load the page  execute the JavaScript  and reload the page  You will then be able to read the  timezone variable and use it to your pleasure  It returns the current UTC GMT time zone offset  GMT -7  or whatever timezone you are in

User · Answer

Here is a robust JavaScript solution to determine the time zone the browser is in   gt  gt  gt  var timezone   jstz determine     gt  gt  gt  timezone name      quot Europe London quot   https   github com pellepim jstimezonedetect

User · Answer

The most popular    standard   way of determining the time zone I ve seen around is simply asking the users themselves  If your website requires subscription  this could be saved in the users  profile data  For anon users  the dates could be displayed as UTC or GMT or some such   I m not trying to be a smart aleck  It s just that sometimes some problems have finer solutions outside of any programming context

User · Answer

I still have not seen a detailed answer here that gets the time zone  You shouldn t need to geocode by IP address or use PHP  lol  or incorrectly guess from an offset    Firstly a time zone is not just an offset from GMT  It is an area of land in which the time rules are set by local standards  Some countries have daylight savings  and will switch on DST at differing times  It s usually important to get the actual zone  not just the current offset   If you intend to store this timezone  for instance in user preferences you want the zone and not just the offset  For realtime conversions it won t matter much   Now  to get the time zone with javascript you can use this    gt  gt  new Date   toTimeString     15 46 04 GMT 1200  New Zealand Standard Time     Use some regular expression to extract the time    However I found it easier to simply use this robust plugin which returns the Olsen formatted timezone   https   github com scottwater jquery detect timezone

User · Answer

Getting a valid TZ Database timezone name in PHP is a two-step process    With JavaScript  get timezone offset in minutes through getTimezoneOffset  This offset will be positive if the local timezone is behind UTC and negative if it is ahead  So you must add an opposite sign to the offset   var timezone offset minutes   new Date   getTimezoneOffset    timezone offset minutes   timezone offset minutes    0   0   -timezone offset minutes    Pass this offset to PHP  In PHP convert this offset into a valid timezone name with timezone name from abbr function      Just an example   timezone offset minutes   -360        GET  timezone offset minutes       Convert minutes to seconds  timezone name   timezone name from abbr      timezone offset minutes 60  false       America Chicago echo  timezone name  lt  code gt  lt  pre gt     I ve written a blog post on it  How to Detect User Timezone in PHP  It also contains a demo

User · Answer

-new Date   getTimezoneOffset   60    The method getTimezoneOffset   will subtract your time from GMT and return the number of minutes  So if you live in GMT-8  it will return 480   To put this into hours  divide by 60  Also  notice that the sign is the opposite of what you need - it s calculating GMT s offset from your time zone  not your time zone s offset from GMT  To fix this  simply multiply by -1    Also note that w3school says      The returned value is not a constant  because of the practice of using   Daylight Saving Time

[html] Determine a user's timezone

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