CODEWITHSUNDEEP
javascriptdatetimecountdown
Matthew Ogborne
Matthew Ogborne

Reputation: 554

Javascript Date using UTC time to correct time to GMT

I have a javascript date such as the one below, which is "now" plus say 20 mins:

var end = new Date('04/14/2013 14:00');

Which is being used in a count down script to this time (a delivery ETA).

However this relies upon the clients machine to work out when the countdown should finish, which may not be in GMT or GMT +1 for daylight saving hours.

I looked at the UTC method here http://www.w3schools.com/jsref/jsref_utc.asp , but frankly got lost.

So my question is:

How can I adjust the variable end to account for a possible time difference between GMT and their local settings on the clients machine so that it can at trusted?

Note: "trusted" is a strong word here, maybe "more likely to be accurate" may be better :) Also this needs to be pure JS no jQuery.

Matt

Upvotes: 1

Views: 1346

Answers (2)

Emissary
Emissary

Reputation: 10148

This perhaps doesn't answer the question directly and maybe I've missed something but it looks like you are over-complicating the problem anyway - if you are using a date as part of a countdown timer then you must always know what the offset (countdown) is at any particular moment.

Since Date Always returns the local time if you do not pass any parameters to the constructor, why not just determine your "end" date client-side based only on your offset. Eg.

var offset = 1000*60*20; // 20 minutes (in milliseconds)
var end = new Date( new Date().getTime() + offset );

This way you never need to worry about the local timezone or even DST.

Upvotes: 0

Bergi
Bergi

Reputation: 665121

I looked at the UTC method, but frankly got lost.

No, using the Date.UTC function is fine and the way to go. In your case, it would be

var end = new Date(Date.UTC(2013, 3, 14, 14, 0)); // notice months are zero-based

Of course you could use the milliseconds since epoch directly, especially if you generate the date value dynamically:

var end = new Date(1365948000000);

Upvotes: 1

Related Questions