I get incorrect results when trying to find numeric difference between two dates:
var startDate = moment( $(\'[name=\"date-start\"]\').val(), \"DD.MM.YYYY\")
the diff method returns the difference in milliseconds. Instantiating moment(diff) isn't meaningful.
You can define a variable :
var dayInMilliseconds = 1000 * 60 * 60 * 24;
and then use it like so :
diff / dayInMilliseconds // --> 15
Edit
actually, this is built into the diff method, dubes' answer is better