period of time

時期(じき)	Period of time of a natural or social phenomenon:the rainy season. The time that you can see fall leaves. The humid time of year. Harvest time. This is the time of year when xxxx is very cheap.

期間(きかん)	A precise period of time that humans made up. (usually several months. or years). Summer vacation. You are forbidden to enter Japan for a period of five years.