How to initialize a JavaScript Date to a particular time zone

Question

I have date time in a particular timezone as a string and I want to convert this to the local time  But  I don t know how to set the timezone in the Date object   For example  I have Feb 28 2013 7 00 PM ET  then I can   var mydate   new Date    mydate setFullYear 2013   mydate setMonth 02   mydate setDate 28   mydate setHours 7   mydate setMinutes 00       As far as I know  I can either set the UTC time or local time  But  how do I set time in another timezone    I tried  to use the add subtract the offset from UTC but I don t know how to counter daylight savings  Am not sure if I am heading the right direction    How can I go about converting time from a different timezone to local time in javascript

User · Answer

For Ionic users  I had hell with this because  toISOString   has to be used with the html template   This will grab the current date  but of course can be added to previous answers for a selected date   I got it fixed using this    x000D   x000D  date   new Date    x000D  public currentDate  any   new Date this date getTime   - this date getTimezoneOffset   60000  toISOString    x000D   x000D   x000D    The  60000 is indicating the UTC -6 which is CST so whatever TimeZone is needed  the number and difference can be changed

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Was facing the same issue  used this one  Console log Date parse  Jun 13  2018 10 50 39 GMT 1      It will return milliseconds to which u can check have  100 timzone intialize British time Hope it helps

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I found the most supported way to do this  without worrying about a third party library  was by using getTimezoneOffset to calculate the appropriate timestamp  or update the time then use the normal methods to get the necessary date and time   var mydate   new Date    mydate setFullYear 2013   mydate setMonth 02   mydate setDate 28   mydate setHours 7   mydate setMinutes 00       ET timezone offset in hours  var timezone   -5     Timezone offset in minutes   the desired offset in minutes  converted to ms     This offset should be the same for ALL date calculations  so you should only need to calculate it once  var offset    mydate getTimezoneOffset      timezone   60     60   1000      Use the timestamp and offset as necessary to calculate min sec etc  i e  for countdowns  var timestamp   mydate getTime     offset      seconds   Math floor timestamp   1000    60      minutes   Math floor timestamp   1000   60    60      hours     Math floor timestamp   1000   60   60       Or update the timestamp to reflect the timezone offset  mydate setTime mydate getTime     offset      Then Output dates and times using the normal methods  var date   mydate getDate        hour   mydate getHours      EDIT  I was previously using UTC methods when performing the date transformations  which was incorrect  With adding the offset to the time  using the local get functions will return the desired results

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Background  JavaScript s Date object tracks time in UTC internally  but typically accepts input and produces output in the local time of the computer it s running on  It has very few facilities for working with time in other time zones   The internal representation of a Date object is a single number  representing the number of milliseconds that have elapsed since 1970-01-01 00 00 00 UTC  without regard to leap seconds   There is no time zone or string format stored in the Date object itself   When various functions of the Date object are used  the computer s local time zone is applied to the internal representation   If the function produces a string  then the computer s locale information may be taken into consideration to determine how to produce that string   The details vary per function  and some are implementation-specific   The only operations the Date object can do with non-local time zones are    It can parse a string containing a numeric UTC offset from any time zone   It uses this to adjust the value being parsed  and stores the UTC equivalent   The original local time and offset are not retained in the resulting Date object   For example   var d   new Date  2020-04-13T00 00 00 000 08 00    d toISOString        gt   2020-04-12T16 00 00 000Z  d valueOf            gt  1586707200000   this is what is actually stored in the object   In environments that have implemented the ECMASCript Internationalization API  aka  Intl    a Date object can produce a locale-specific string adjusted to a given time zone identifier   This is accomplished via the timeZone option to toLocaleString and its variations   Most implementations will support IANA time zone identifiers  such as  America New York    For example   var d   new Date  2020-04-13T00 00 00 000 08 00    d toLocaleString  en-US     timeZone   America New York         gt   4 12 2020  12 00 00 PM      midnight in China on Apring 13th is noon in New York on April 12th    Most modern environments support the full set of IANA time zone identifiers  see the compatibility table here    However  keep in mind that the only identifier required to be supported by Intl is  UTC   thus you should check carefully if you need to support older browsers or atypical environments  for example  lightweight IoT devices     Libraries  There are several libraries that can be used to work with time zones   Though they still cannot make the Date object behave any differently  they typically implement the standard IANA timezone database and provide functions for using it in JavaScript   Modern libraries use the time zone data supplied by the Intl API  but older libraries typically have overhead  especially if you are running in a web browser  as the database can get a bit large   Some of these libraries also allow you to selectively reduce the data set  either by which time zones are supported and or by the range of dates you can work with   Here are the libraries to consider   Intl-based Libraries  New development should choose from one of these implementations  which rely on the Intl API for their time zone data    Luxon  successor of Moment js  date-fns-tz  extension for date-fns    Non-Intl Libraries  These libraries are maintained  but carry the burden of packaging their own time zone data  which can be quite large    js-joda timezone  extension for js-joda  moment-timezone   extension for Moment js  date-fns-timezone  extension for older 1 x of date-fns  BigEasy TimeZone tz js     While Moment and Moment-Timezone were previously recommended  the Moment team now prefers users chose Luxon for new development   Discontinued Libraries  These libraries have been officially discontinued and should no longer be used    WallTime-js TimeZoneJS   Future Proposals  The TC39 Temporal Proposal aims to provide a new set of standard objects for working with dates and times in the JavaScript language itself   This will include support for a time zone aware object

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Building on the answers above  I am using this native one liner to convert the long timezone string to the three letter string   var longTz    America Los Angeles   var shortTz   new Date        toLocaleString  en    timeZoneName   short   timeZone  longTz        split           pop      This will give PDT or PST depending on the date provided   In my particular use case  developing on Salesforce  Aura Lightning   we are able to get the user timezone in the long format from the backend

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I ran into a similar problem with unit tests  specifically in jest when the unit tests run locally to create the snapshots and then the CI server runs in  potentially  a different timezone causing the snapshot comparison to fail   I mocked our Date and some of the supporting methods like so    describe             gt      let originalDate     beforeEach      gt        originalDate   Date      Date   jest fn         d    gt            let newD          if  d              newD    new originalDate d              else             newD    new originalDate  2017-05-29T10 00 00z                       newD toLocaleString        gt              return  new originalDate newD valueOf     toLocaleString  en-US    timeZone   America New York                        newD toLocaleDateString        gt              return  new originalDate newD valueOf     toLocaleDateString  en-US    timeZone   America New York                        newD toLocaleTimeString        gt              return  new originalDate newD valueOf     toLocaleTimeString  en-US    timeZone   America New York                        return newD                     Date now        gt    return  Date                 afterEach      gt        Date   originalDate

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Maybe this will help you   x000D   x000D      x000D     Shift any Date timezone  x000D      param  Date  date - Date to update  x000D      param  string  timezone - Timezone as  -03 00   x000D      x000D  function timezoneShifter date  timezone    x000D    let isBehindGTM   false  x000D    if  timezone startsWith  -      x000D      timezone   timezone substr 1   x000D      isBehindGTM   true  x000D      x000D   x000D    const  hDiff  mDiff    timezone split      map  t    gt  parseInt t    x000D    const diff   hDiff   60   mDiff    isBehindGTM   1   -1   x000D    const currentDiff   new Date   getTimezoneOffset    x000D   x000D    return new Date date valueOf      currentDiff - diff    60   1000   x000D    x000D   x000D   x000D   x000D  const  now   new Date   x000D  console log  x000D      x000D       Here       now toLocaleString    x000D       Greenwich      timezoneShifter  now   00 00   toLocaleString    x000D       New York      timezoneShifter  now   -04 00   toLocaleString    x000D       Tokyo      timezoneShifter  now    09 00   toLocaleString    x000D       Buenos Aires      timezoneShifter  now   -03 00   toLocaleString    x000D      join   n   x000D     x000D   x000D   x000D

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This should solve your problem  please feel free to offer fixes  This method will account also for daylight saving time for the given date   dateWithTimeZone    timeZone  year  month  day  hour  minute  second    gt      let date   new Date Date UTC year  month  day  hour  minute  second       let utcDate   new Date date toLocaleString  en-US     timeZone   UTC         let tzDate   new Date date toLocaleString  en-US     timeZone  timeZone        let offset   utcDate getTime   - tzDate getTime       date setTime  date getTime     offset       return date       How to use with timezone and local time   dateWithTimeZone  America Los Angeles  2019 8 8 0 0 0

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I know its 3 years too late  but maybe it can help someone else because I haven t found anything like that except for the moment-timezone library  which is not exactly the same as what he s asking for here   I ve done something similar for german timezone  this is a little complex because of daylight saving time and leap years where you have 366 days   it might need a little work with the  isDaylightSavingTimeInGermany  function while different timezones change on different times the daylight saving time   anyway  check out this page  https   github com zerkotin german-timezone-converter wiki  the main methods are   convertLocalDateToGermanTimezone convertGermanDateToLocalTimezone  I ve put an effort into documenting it  so it won t be so confusing

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For mumbai time diffrence is 5 5 hrs so    city time diff 5 5  change according to your city    let timee  Date now       timee timee  3600000 city time diff     Add our city time  in msec       let new date new Date timee  console log  quot My city time is   quot  new date

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As Matt Johnson said  If you can limit your usage to modern web browsers  you can now do the following without any special libraries  new Date   toLocaleString  quot en-US quot    timeZone   quot America New York quot      This isn t a comprehensive solution  but it works for many scenarios that require only output conversion  from UTC or local time to a specific time zone  but not the other direction    So although the browser can not read IANA timezones when creating a date  or has any methods to change the timezones on an existing Date object  there seems to be a hack around it   x000D   x000D  function changeTimezone date  ianatz          suppose the date is 12 00 UTC   var invdate   new Date date toLocaleString  en-US         timeZone  ianatz              then invdate will be 07 00 in Toronto      and the diff is 5 hours   var diff   date getTime   - invdate getTime          so 12 00 in Toronto is 17 00 UTC   return new Date date getTime   - diff      needs to substract        E g  var here   new Date    var there   changeTimezone here   America Toronto     console log  Here    here toString    nToronto    there toString       x000D   x000D   x000D

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Try  date-from-timezone  it resolves expected date with help of natively available Intl DateTimeFormat   I used that method in one of my projects for few years already  but it s now I decided to publish it as small OS project

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You can specify a time zone offset on new Date    for example   new Date  Feb 28 2013 19 00 00 EST     or  new Date  Feb 28 2013 19 00 00 GMT-0500     Since Date store UTC time   i e  getTime returns in UTC    javascript will them convert the time into UTC  and when you call things like toString javascript will convert the UTC time into browser s local timezone and return the string in local timezone  i e  If I m using UTC 8    gt  new Date  Feb 28 2013 19 00 00 GMT-0500   toString    lt   Fri Mar 01 2013 08 00 00 GMT 0800  CST     Also you can use normal getHours Minute Second method    gt  new Date  Feb 28 2013 19 00 00 GMT-0500   getHours    lt  8     This 8 means after the time is converted into my local time - UTC 8  the hours number is 8

User · Answer

I had the same problem but we can use the time zone we want we use  toLocaleDateString   eg   x000D   x000D  var day new Date    const options   day  numeric   month  long   year  numeric   timeZone  Asia Kolkata    const today day toLocaleDateString  en-IN   options   console log today   x000D   x000D   x000D

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Try using ctoc from npm  https   www npmjs com package ctoc timezone  It has got simple functionality to change timezones  most timezones around 400  and all custom formats u want it to display

[javascript] How to initialize a JavaScript Date to a particular time zone

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