We measure time using clocks and calendars in units like seconds, minutes, hours, days, weeks, months and years. A day has 24 hours, with A.M used to indicate times from midnight to noon and P.M. used for times from noon to midnight.

2. We measure time in seconds, minutes, hours, days, weeks, months
and years with clocks and calendars.
A day has 24 hours. We use A.M to tell time running
from midnight to noon and P.M. for time running from noon to
midnight.