@marcusmachiavelli,
What is interesting about the measuring of time is that some cultures have built monuments to measure the number of days, hours, and minutes (and seconds today made exact by the atomic clock), that were built thousands of years ago that are very accurate. Calendars created by different cultures have different number of days and years.
It's true that time is a man-made concept, but the majority of humans follow its measurements in one form or another.
What's also interesting is that our body clock can often work to get us up in the morning.