Memory used to be REALLY expensive. Cutting the length of your programs down as much as possible was necessary. Thus, it became standard to save the date using two digits for the day, two digits for the month, and two digits for the year. Turns out going from the year 99 to the year 00 could cause some problems if your program isn’t designed to expect it.
I saw someone setting up a few kegs of beer to give to the parents the day before trick or treat in my neighborhood. <3