Sundials are also responsible for why we say “o’clock”. It’s a differentiatior. Because the speed of a sundial would vary based on the time of year while a clock was constant, you had to clarify what kind of time you were talking about. Did you mean 10 of the clock or 10 of the sun? (Basically no one said o’sun, if you didn’t specify, it was assumed you meant by the sun.) Somehow, that stuck around long after sundials fell out of common use.