timekeeper

Concise Oxford English Dictionary © 2008 Oxford University Press:
timekeeper/ˈtʌɪmkiːpə(r)/

▶noun

• 1 a person who records the amount of time taken by a process or activity.

• 2 a person regarded in terms of their punctuality.

  ■ a watch or clock regarded in terms of its accuracy.

• 3 archaic a clock.

– derivatives
timekeeping noun.