Timekeeping (day length): The length of a civil day is determined in which terms? Focus on how the 24-hour day is defined for calendars and clocks. Choose the correct option.

Concept/ApproachAn astronomical unit (AU) measures distance (Earth–Sun). A solar day is based on the apparent motion of the Sun—i.e., solar terms. “Length of the hours” is derivative, not the defining standard; hours are subdivided from the solar day.

Final AnswerSolar terms