Before alarm clocks became popular, British workers called “knocker uppers” were hired to tap on windows to wake people up in the morning.

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22 Questions About Time and Timekeeping Answered

Humans, arguably, have been measuring time ever since they began tracking the rising and setting of the Sun. That means horology—the study of time’s measurement—has a very long history. This list is a brief horological primer. Earlier versions of these questions and answers first appeared in the