Time is something that helps us keep track of our lives including things in the past, present, and future. Before, people used the sun and the cycle of the moon to tell the time. After many different contraptions were invented to measure time, advanced clocks, such a quartz crystal clocks, and atomic clocks were invented that help us keep track of time. It is not the same time all over the world--each part of the world is in a different time zone.