I am creating a date in node js, my server is in IST, I want to determine if the date would come PDT or PST (i.e. If the Daylight saving is on or off). If my server was in PST/PDT time it would be automatically decide. Is there any way I can determine this?
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1Not for future dates. The rules can change. – David Schwartz Jan 23 '14 at 12:44
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how about past dates? when i create new Date("dateString") it's able to decide PST or PDT if my system time is in PT. I want to do the same from IST system time. – Neo Jan 23 '14 at 12:50
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1The answer in the dup post is one way. Another would be using the `isDST` function from [moment.js](http://momentjs.com) – Matt Johnson-Pint Jan 26 '14 at 06:07
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After creating the date with ...Date()
you are able to retrieve the timezone offset of the client with ...getTimezoneOffset()
. You can not tell whether the client is in DST or not, but you have the absolute amount to GMT/UTC. Or, you can further retrieve the time a UTC timestamp and convert that to whatever you want on the server.

Axel Amthor
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I will get a date string "10/23/2014 00:00:00" that is from PT. I send to a client which may be in any time zone but i want to determine that day on PT was daylight saving on or not. – Neo Jan 23 '14 at 12:59
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Convert to UTC timestamp in milliseconds, send that to the client and create the date from milliseconds instead of a formatted string. Whatever timezone with or w/o DST the client is in, the date will be proper, since it's set from UTC: `ndate = new Date(); ndate.setTime(UTCinMillisFromServer);` – Axel Amthor Jan 23 '14 at 13:05
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What if the local machine is in a different timezone (not PST or PDT)? – Aniket Suryavanshi Oct 29 '18 at 07:12
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Actually that doesn't matter at all: submit UTC and the client will transform in his TZ, regardless which one this is and whether it has or not DST etc. – Axel Amthor Oct 31 '18 at 11:05