Date picker control in Properties dialog?

Hi. How do we enable a date picker dialog for a date field in a tab on the Properties dialog? (Web UI and client UI.)

Can we disable the field and force users to use the date picker control?

If we leave the field enabled, does the date picker reflect the manually entered date? What if the date isn't valid?

How do we force the date display in the final date field to follow a certain format? (I prefer yyyy-mm-dd like all good people, but the client wants a different date format.)