JavaScript to find the error in a simple script

In the attached file there is a simple ready to use script that displays the difference in days between two dates. The counting works in Chrome and Opera. But in Firefox, IE and Safari instead of a number, output is NaN (not a number). The essence of the job is to correct/to fix the script to correctly display the number of days in all browsers.

PS: the date format that gets the script at the input DD.MM.YYYY (not otherwise).