I am not going to be able to find proof 18 years later but ...
1979 was 79, the next year added 1 to 9, reset to 0, and carried thje 2nd digit getting 80. same with 89 to 90, but with 99 it went to :0
This was this function that was either part of the cb80/lk80 package or early dos. aka cbasic circa 1980s
It still runs today on my XP as long as i set the clock back. Once the program initializes, I can restore the clock while I run it.
” with 99 it went to :0”
Nope. Date functions did it work that way. Date functions would store 2000 as “00” which the computer could not determine it was 2000.