If you'd like to make a note about your employee's birthdays we propse the following two options for you:
Add Day Note
The Day Note is visible at the top of the Hourline Day, on the Toolbox > Calendar > Day, in the Long Form and the Web Access Tiers.
You can also Import a list of Day Notes to set all birthdays in one go.
Add Birthday Calendar Object
In Object Manager, select a Type and add a new Object: Birthdays (Causes Conflict = No)
Add the Object to the Hourline View. Book the Object and add the person's name as "header".