時代
じだい · jidai · JLPT N4 · noun
age
⏳ 時代 = time (時) + generation (代): the time of a generation
時 (ji) means time or hour, as in 時間 (jikan). 代 (dai) means generation or a span that replaces the last, as in 世代 (sedai). Together: the stretch of time belonging to one generation, i.e. an era, as in 江戸時代 (Edo jidai).
代 — person radical 亻 + 弋 (stake/dart, phonetic)
代 is a semantic-phonetic compound: 亻 (person) gives the meaning and 弋 supplies the sound. The original sense was one person taking the place of another, which broadened to 'substitute,' 'replace,' and then 'generation' or 'era' — successive groups of people replacing the previous.