How do you make the datepicker's standed form longer

How do you make the datepicker's standed form longer

I need to make length of the datepicker's input form, large enough to display the date format    am using
 
$.datepicker.setDefaults({dateFormat: 'DD, d  MM yy' , minDate: -0, maxDate: "+1M +05D"  });
 
Cant make it work with AltField and size of the field,, and i am not using a custom css