日期
rìqí · HSK 1
date
📅 日 (sun/day) + 期 (period) = date / scheduled day
日 means sun or day; 期 means a fixed period or appointed time. Together 日期 literally reads as day-period, i.e. a calendar date. 期 also shows up in 星期 (week) and 学期 (semester), reinforcing the period sense.
日 — pictograph of the sun
日 is a pictograph of the sun, originally drawn as a circle with a dot or stroke inside representing the sun's substance. Over time the round shape was squared off into the modern rectangular form. It means 'sun' and by extension 'day'.
期 — 其 (phonetic) + 月 (moon/time)
期 is a phono-semantic compound. The right side 月 (moon) signals meaning, since lunar cycles marked fixed time periods in ancient China. The left side 其 supplies the sound. Together it points to a set time, period, or appointed date — meanings still carried today in words like 期间 and 日期.