period, time, date, term
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期 centers on a defined span of time: a period, a set date, or a term. It marks when something is expected or scheduled to happen.
period; term; interval
expectation; anticipation; hope
time; season; period; phase; stage
fixed period; fixed term
early days; early years; early stages; initial stages; beginning
term; period; time frame
long-term
same period; corresponding period
postponement; deferment; adjournment
short-term
early stage
latter period; second half; late stage; third trimester; second semester
last years; closing years; last days; closing days; end; last stage; final stages; terminal stage (of a disease)
a period (of time)
short term; short time
one's last moment; one's death; one's end
school term; semester
first term; first half-year; preceding period; early period
cycle; period
next term; next period
the present term; the present session
term of office
middle period
ground-breaking; revolutionary; unprecedented; epoch-making
期 combines 其 (a winnowing basket, here used phonetically for キ) with 月 (moon/month), suggesting a period of time marked by the moon. The modern form retains this phono-semantic structure.
The left side 其 looks like a basket, and the right side 月 is the moon. Imagine a basket used to collect moons, each one marking a new period or term.
For キ, picture a key that unlocks a new time period: key -> キ, and the moon marks the start of the term.