How to get start and end of day in Javascript?

How to get start ( 00:00:00 ) and end ( 23:59:59 ) of today in timestamp ( GMT )? Computer use a local time.

Answer

var start = new Date();
start.setUTCHours(0,0,0,0);

var end = new Date();
end.setUTCHours(23,59,59,999);

alert( start.toUTCString() + ':' + end.toUTCString() );

If you need to get the UTC time from those, you can use UTC().