It’s odd that we measure most things aeronautical in time, not distance or even speed. The relationship of time to aviation regulation is fundamental and is the basis for nearly all rules that govern pilots and the operation of aircraft. Log the time and you’re legal to fly, but don’t forget to check the calendar as well as the flight hour meter.
Perhaps the first time restriction a student pilot has to face is the limit on solo privileges. When your instructor endorses your student certificate to allow you to fly the airplane on your own, the solo endorsement is good for only 90 days. After 90 days you can’t continue to fly solo until your instructor has renewed your privilege by again endorsing your certificate [FAR 61.87 (n)].
