How to calculate days from two dates in report

I have found the solution for this


function days_between(date1, date2) {

// The number of milliseconds in one day
var ONE_DAY = 1000 * 60 * 60 * 24

// Convert both dates to milliseconds
var date1_ms = date1.getTime()
var date2_ms = date2.getTime()

// Calculate the difference in milliseconds
var difference_ms = Math.abs(date1_ms - date2_ms)

// Convert back to days and return
return Math.round(difference_ms/ONE_DAY)

}