What is the lease termination date to calculate penalty?

A tenant wants to terminate his 9-year lease. There is a 3 months notice period.

Lease started on June 1st, 2021.

Tenant informed his landlord on February 20th 2023. Tenant will leave on May 15th 2023.

What dates shall be taken into account to calculate the penalty for ending the lease within the 3 first years? How many months will be the penalty amount?

Thanks