Nice digits. 1776
You can only be elected to a maximum of two four-year terms as president; and if you've served out another's term for more than 2 of those years, you can only be elected to 1 ferm afterwards.
Therefore, for Trump to get max legal chair time, he could conceivably serve out just less than 2 years of Biden's remainder and still be eligible to be elected to second four-year term.
That means that anytime after January 21st, 2023 Trump could occupy the oval office as president and still run for and serve another four-year term as president. Legally.