Shopper fields (Date), change to other calendars, Add Proper DOB

[mhshakouri]

I'm using VM 3.0.3 ,
I want to use a shopper field for DOB ( Date of birth)
Well I need a guide to add a DOB field, not an age checker of course.
And I also need to change the calendar to Shamsi (solar) Calendar, or better say, Iranian Calendar. Is that possible? Where is it reading the calendar from?