The Mesopotamians invented time, the calendar, and the sundial.  The calendar was invented when people created it through the 12 lunar phases of the moon.  Since their mathematical system was based on the number 60, there were 60 seconds in a minute, there were 60 minutes in a hour.  They invented the sundial because they figured out that shadows move when the sun moves.  The Mesopotamians used all these time units to predict the future and floods.