Adding hours to JavaScript Date object?

javascript datetime

Jeff Meatball Yang · Jun 26, 2009 · Viewed 541.4k times · Source

It amazes me that JavaScript's Date object does not implement an add function of any kind.

I simply want a function that can do this:

var now = Date.now();
var fourHoursLater = now.addHours(4);

function Date.prototype.addHours(h) {

   // how do I implement this?  

}

I would simply like some pointers in a direction.

Like this:

new Date(milliseconds + 4*3600*1000 /*4 hrs in ms*/)?

This seems really hackish though - and does it even work?

Answer

JavaScript itself has terrible Date/Time API's. Nonetheless, you can do this in pure JavaScript:

Date.prototype.addHours = function(h) {
  this.setTime(this.getTime() + (h*60*60*1000));
  return this;
}