Calculate difference between 2 timestamps using javascript

Question

I have to calculate the difference between 2 timestamps. Also can you please help me with conversion of a string into timestamp. Using plain javascript only. NO JQUERY.

Answer 1

Based on the approved answer:

function(timestamp1, timestamp2) {
    var difference = timestamp1 - timestamp2;
    var daysDifference = Math.floor(difference/1000/60/60/24);

    return daysDifference;
}