Convert one timezone to another in javascript

1
votes

I'm looking for a function that receives a time, source timezone and a destination and returns time in the destination timezone

timezones are in the following format: 'utc', 'est', 'edt', 'gmt', ...

function convertTime(time,fromZone,toZone){
   // do conversion
   return convertedTime;
}
2
javascriptdatetimetimezonetimezone-offsetmoment-timezone
I suggest you use a moment.js library. – Hirasawa Yui
@HirasawaYui I know moment but couldn't find how to do what I'm looking for with moment and i see timezones in moment are in this format for example "America/New_York" and not "est" – user4092086
@user4092086—you could create your own map of abbreviations to IANA representative locations, however you need a strategy for dealing with ambiguous abbreviations (such as EST and CST). Also, different places in a timezone may have different rules for daylight saving, hence IANA's choice of representative locations rather than the broader timezone designators (though the concept of "timezone" is changing to align with IANA's approach). – RobG

2 Answers

2
votes

Sorry, but it is not possible to convert between time zones in the way you describe, for several reasons:

  • Many time zone abbreviations are ambiguous. For example, CST could be Central Standard Time, Cuba Standard Time, or China Standard Time. IST could be India Standard Time, Israel Standard Time, or Irish Summer Time. There are many other examples.

  • Not everyone agrees on what the abbreviations for time zones should be. For example, in Hawaii, both HST and HAST are commonly used.

  • Not all time zone abbreviations are in English. For example, HNE and HAE are French time zones abbreviations used for the Eastern time zone in Canada.

  • Not all time zones have abbreviations in the way we think about them. For example, there are two time zones in Kazakhstan. In the western part of the country they are 5 hours ahead of UTC. In the eastern part of the country they are 6 hours ahead of UTC. In the past, English speakers have assigned made-up abbreviations such as AQTT or ORAT to the west, and ALMT to the east, after the names of some major cities, but none of those are actually used there nor ever have been.

  • Assuming EST and EDT are Eastern Standard Time and Eastern Daylight Time as observed in the US and Canada, you would have to predetermine whether to pass EST or EDT to your function depending on which was in effect at the time given. For example, if you passed a time on today, 2013-03-13 and used EST, you would be in error since EDT is currently in effect. This would apply for both fromZone and toZone, and each would have to be determined independently.

  • Say you tried to write logic to address the previous point. You would still have problems where two different time zone abbreviations apply to different parts of the same time zone at the same time. For example, right now MDT applies to most of the US Mountain time zone - except most (but not all) of Arizona where MST applies.

All of the above factors and more are considered by using IANA tz database identifiers, such as America/New_York, instead of abbreviations.

I also suggest reviewing the following resources:

1
votes

Here's a good StackOverflow past-post about this general subject:

How to initialize a JavaScript Date to a particular time zone