If your goal is to have a full fledge calendar, mr_vodka is absolutely right.
If you want to display a small calendar instead of a textual date, the SeedCode calendar has code to display such data. You will need to extract it for your purpose and code it into your solution for each field.
If you want to display a calendar for users to select a date and can live with the date being textual, FileMaker fields can display a date during data entry. This is one of the available field formats.