If you see a two-digit number beginning with 1, drop the first number and subtract two from the second number. If your sum is negative, it’s that many hours before noon.
If your number begins with 2, do the same thing. If your number is negative, it’s that many hours before 10pm.
AnUnusualRelic@lemmy.world 2 hours ago
You’d get that instinct within at most a week though.