My childhood "cipher" for converting 24‑hour time to 12‑hour (and I still use it)
Ever since I was a kid, I’ve been converting PM hours in my own weird way – not by subtracting 12, but by a rule my brain invented on its own. And the funny thing? I had no idea that “subtract 12” was even a thing – school never taught it, and my parents just said “4 in the afternoon” without explaining the mechanics. So my little brain, faced with 13:00, 14:00, etc., started searching for patterns and came up with this:
· For 13:00 to 21:00:
Subtract 2 from the number (e.g., 13 – 2 = 11, 14 – 2 = 12, … 21 – 2 = 19).
Then remove the leading digit (which is always a 1) – you get 1, 2, 3 … 9.
So: 13:00 → 1, 14:00 → 2, … 21:00 → 9.
· For 22:00, 23:00 and 24:00:
I just slapped a “10” in front because I intuitively knew these were 10, 11, 12 PM.
So: 22:00 → 10, 23:00 → 11, 24:00 → 12.
That gave me a full dial:
13→1, 14→2, … 21→9, 22→10, 23→11, 24→12.
And for the morning hours (1:00 to 12:00) I counted normally – no tricks.
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Now, the cool part – why “subtract 2 and remove a 1”?
My brain had accidentally rediscovered basic algebra without knowing it.
The real conversion is X – 12 = Y. But I broke it into X – 2 – 10 = Y.
Subtracting 2 was easy, and “removing the leading 1” was just subtracting 10 (since numbers like 11, 12, … 19 are 10 + something). So my child‑mind split the hard subtraction into two simple steps that felt natural. For 22‑24, I just followed the obvious sequence after 9.
Best part? I’m an adult now, I know the correct subtraction, but my brain still runs this algorithm automatically every time I see 16:00 or 21:00. It’s instant, subconscious – zero delay. But trying to explain it out loud? Total disaster. “Subtract 2, drop the 1, and for 22 just think 10…” – people look at me like I’m from Mars. So I just say “meet at 16:00” to others, while secretly running my personal cipher in my head.
This has been my private time‑translation protocol for over 20 years, and it’s never failed. I’ll probably die with it 😄
P.S. Anyone else have a weird childhood counting system they still use?