Why do we still say 'o'clock'?
Dial it back a bit!
Why do we use ‘o’clock’ when telling the time?
When mechanical clocks were first introduced in the 14th century, the most common way to tell time was using a sundial - which often showed a different time than the mechanical clock.
Saying ‘of the clock’ (later shortened to ‘o’clock’) let someone know which version of time you meant.
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Image credits: "sundial" by Muffet is licensed under CC BY 2.0