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.
Only inasmuch as I have to count from 12 because I don’t have the built-in instinct for that time format.
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.
Anything to not subtract 12