Timi was born in $1999$. Ever since her birth how many times has it happened that you could write that day’s date using only the digits $0$, $1$ and $2$? For example, $2022.02.21$. is such a date.
Problem
Source: (2022-) 2023 XVI 16th Dürer Math Competition Finals Day 2 E2
Tags: number theory, combinatorics