Whenever you Open a New Database, MM will ask you to specify the Age-Up-Date to use to calculate each Athlete's age. That way when you enter an Athlete's birth date, MM will automatically calculate his/her age.
If later you find that you want to change the Age-Up-Date and have MM recalculate each Athlete's Age based on this new Age-Up-Date, click on File from the Main Menu Bar and then Set-up and then Meet Setup. Now you may change the Age-Up-Date and then click the Age-Up Athletes button at the bottom to recompute all athlete ages.
