Convert UTC Epoch to local date

Question

I have been fighting with this for a bit now. I’m trying to convert epoch to a date object. The epoch is sent to me in UTC. Whenever you pass new Date() an epoch, it assumes it’s local epoch. I tried creating a UTC object, then using setTime() to adjust it to the proper epoch, but the only method that seems useful is toUTCString() and strings don’t help me. If I pass that string into a new date, it should notice that it’s UTC, but it doesn’t.

new Date( new Date().toUTCString() ).toLocaleString()

My next attempt was to try to get the difference between local current epoch and UTC current epoch, but I wasn’t able to get that either.

new Date( new Date().toUTCString() ).getTime() - new Date().getTime()

It’s only giving me very small differences, under 1000, which is in milliseconds.

Any suggestions?

Answer 1

Epoch time is in seconds from Jan. 1, 1970. date.getTime() returns milliseconds from Jan. 1, 1970, so.. if you have an epoch timestamp, convert it to a javascript timestamp by multiplying by 1000.

   function epochToJsDate(ts){
        // ts = epoch timestamp
        // returns date obj
        return new Date(ts*1000);
   }

   function jsDateToEpoch(d){
        // d = javascript date obj
        // returns epoch timestamp
        return (d.getTime()-d.getMilliseconds())/1000;
   }