When you run the frame containing a calendar field, it initially appears with the current day, month, and year selected:

You can change the current day displayed by clicking any of the dates in the calendar. Use the up and down arrow buttons next to the current month and year to increment or decrement their display.

The calendar field functionality is based on the Calendar_Object user class, which handles its processing. For more information about the Calendar_Object user class, see the appendix "Generated User Classes" in the Language Reference Guide.