from unixtimestamp to dd/mm/yyyy hh:mm:sss

Classic Servoy
1

I need to access a solution build with php. The date-fields are integer values as unixtimestamp (milliseconds since 1/1/1970).
I would like to show these fields as a normal datefield or use a second calculated field to show the date as cleartext.

I used:
datereturned.getUTCDate(unixtimefield);
return datereturned;

but that does not work.

I need a method to put the normal datefield back into the unixtimestamp as well.
I looked at the manual but the date-section is not mentioned.
Any ideas?