Timekeep

Thus, the difficulty retarded persons experience with focusing and/or maintaining their attention toward a relevant stimulus dimension (Fisher & Zeaman, 1973) may well hinder their ability to timekeep and predict temporal intervals.

Source: wiktionary

This exercise takes about forty-five minutes. Arrange for someone to timekeep.

Source: wiktionary

Timekeeping is very important, so it is advisable to appoint a responsible and reliable person whose only job is to timekeep.

Source: wiktionary

I broke my watch on the first day and so was obliged to timekeep according to the sun;

Source: wiktionary