add days to unix date

[adishardis]

Two questions,

How do I create a unix timestamp from a date variable derived like this:
var myDate = $(this).data('date');
the format is like this: 2013-01-01

and how do i then create a new unix timestamp for 90 days later than myDate?

Thanks

[adishardis]

Ok, don't know it if it's the practise but here's how I solved it:

        var myDate = $(this).data('date');
        var unixtimestart = new Date(myDate).getTime();
        var enddate = Date.parse(myDate).add(90).days();
        var unixtimeend = new Date(enddate).getTime();