If the field content belongs to a time/date field, you can click on the down-arrow at the far right, or press CTRL+ENTER to see the built in calendar:
You can use the calendar as an aid to find a correct date.
Note that the calendar editor doesn't support time-value editing. In the sample above, the calendar will only change the date-value (24.02.2004), and the time-value (10:19:00) will stay the same when you press ENTER.
The calendar editor can't handle time/date ranges either.You have to edit them manually directly in the line!