Mental arithmetic is in fact not universal. People who grew up on 24h time have the benefit of rote memorizing the relationship between 17 and 5 from childhood.
Like, the fact that 9:00 (or 21:00) points leftward / “west” with the hour-hand is something that kids just have to learn and remember. At first it is a lot of mental overhead. But I bet it was immediate for you when you read this, no?
Mental arithmetic is in fact not universal. People who grew up on 24h time have the benefit of rote memorizing the relationship between 17 and 5 from childhood.
Like, the fact that 9:00 (or 21:00) points leftward / “west” with the hour-hand is something that kids just have to learn and remember. At first it is a lot of mental overhead. But I bet it was immediate for you when you read this, no?