It is a matter of not identified birthday dates. 

Birthdays are not identified as birthday dates if there's no link to the contact. This is very often the case if the birthday dates are created manually or if they are imported.

This is the background: To make the age visible in the calendar the program has to know to which contact the birthday date belongs to. If there's no link to a contact, this information lacks.

In this case please delete the birthday entries by using the function Delete birthdays in calendar. Before using this function an additional dialog opens. Please activate there the option All, which are not present in contacts too. Warning: Please do that only if you are sure that all birthday entries are stored in the contacts. If this is not the case these dates are lost (but you'll find them in the folder Deleted Items).

If there are more birthday dates that are not recognized by the program, please first delete all birthday dates manually and then ask the program to renew them. Take the following steps to do that:

• Switch the view of the calender to By Category (View -> (Arrange By ->) Current View -> By Category)
• Sort the dates by subject
• Highlight the first birthday of the list, press the SHIFT button and then highlight the last birthday
• Release the SHIFT button and press the DEL button
• Now start the program and choose the action Create birthdays on the register Processing. Then highlight the folder contacts and set the Selection to Only actual folder (if required the selection can also be adapted).
• Click on the cogwheel button to start the process

Now the birthday dates are renewed and recognized by the program.