Date of birth Variable

Hi all,

I was wondering if anyone could help with this. I'm creating an e-learning for nursing students and the 'patient' in the activity is 30 years old. Is it possible to have the date of birth (DOB) variable update to show the correct DOB year, no matter when the student completes the e-learning?
E.g if patient is 30 y/o and birthday is 12 May and they did the e-learning on 12 May 2021 the DOB variable will show 12 May 1991 but if they did this e-learning again next year on 12 May 2022, the DOB variable will show 12 May 1992.

I appreciate any help or support on this. Many thanks!