var date_now = unixtimestamp;
var date_future = unixtimestamp;
Just figure out the difference in seconds (don't forget JS timestamps are actually measured in milliseconds) and decompose that value:
// get total seconds between the times var delta = Math.abs(date_future - date_now) / 1000; // calculate (and subtract) whole days var days = Math.floor(delta / 86400); delta -= days * 86400; // calculate (and subtract) whole hours var hours = Math.floor(delta / 3600) % 24; delta -= hours * 3600; // calculate (and subtract) whole minutes var minutes = Math.floor(delta / 60) % 60; delta -= minutes * 60; // what's left is seconds var seconds = delta % 60; // in theory the modulus is not required
EDIT code adjusted because I just realised that the original code returned the total number of hours, etc, not the number of hours left after counting whole days.