Hi @AmoryBodyArts.

At this time there isn't a way to require customers to enter their date of birth before booking an appointment. I see how that would be useful for some business types and I'll share your interest in that feature with the Appointments Team! 

In the meantime, as a workaround, you could add a note in the service description that customers should provide their date of birthy in the Appointment Notes at time of booking. 

You'll be able to see that note from your Appointments Calendar and manually enter customer information to the Customer Directory if you'd like to keep it on file The steps to add your customers birthday to their profile are in this Community post.

Hope this workaround helps for the time being! Let me know if you have any other questions.