Or you could just set your clock back to 1992, as that year is the same, calendar-wise, as 2020 - and would gain you another 28 years before you'd have to reset again. (Or even set to 1964 or even 1936, same thing, only longer reset-period.)

That's the joy of the calendar system we use, there are only so many variations possible. (Seven non-leap-year and seven leap-year.) Which means calendars repeat themselves on a 28-year (7*4, the interval between repeating leap years,) basis - the non-leap-years repeat themselves even more often, but leap years are a good basis, because it guarantees you won't accidentally slip in or out of the leap year cycle. Which is why it's a good thing 2020 (a leap year) is the first not-possible year on a Mac. You just have to reset back to an equivalent leap-year calendar.