Change format of date

I have a datefield in my form, and upon submitting the form I get the value of that datefield and put it into the subject field of the e-mail, something like this:

var myDate = Main_subform.subform1.startDate.rawValue;

var mail = "mailto: test [at] test [dot] com?subject=This is the subject on " + myDate;

And the date presented in the subject field is YYYY-MM-DD, which I guess is the standard. I wish to present the date as DD.MM.YYYY, how can I achieve this? I've tried a few things, but it doesn't turn out right, probably because I'm not using the right syntax or using the functions in the wrong way..