Where the cutoff between 19XX and 20XX happens
This sets where the century change happens. By default, it is 38, that is, 2 digit years before 38 will be assumed to refer to 2000-2037, and years after will be assumed to refere to 1938-1999.
If “afterToday” is true, all years are assumed to be 20XX. The same would be true if this were set to 100+