Several parts combine into one character.

The character for "calendar" is one of the most visually divergent across CJK. Traditional 曆 is a phonetic-semantic compound: 厤 (lì, "succession of grain stalks / orderly arrangement") + 日 (sun / day). The original meaning was "the orderly record of sun and moon cycles" = calendar. The three regions then took different paths: Korea retains 曆, Japan adopted shinjitai 暦, Mainland China simplified to 历. One concept, three shapes — a paradigmatic CJK divergence case.

Korean reading "ryeok" (or "yeok" word-initially). 陽曆 (yangnyeok, solar calendar — Western Gregorian calendar), 陰曆 (eumnyeok, lunar calendar — traditional Korean lunar calendar still used for major holidays like Seollal and Chuseok), 西曆 (seoryeok, "Western calendar" = AD/CE dating system), 還曆 (hwallyeok, "returning calendar" = the 60th birthday — when one completes the full cycle of the 60-year sexagenary calendar and returns to the same year-name as one's birth), 萬歲曆 (manse-ryeok, "ten-thousand-year calendar" = perpetual calendar — used by Korean fortune-tellers).

Mandarin lì, 4th tone (simplified 历). And here Mandarin made a consequential simplification merge: 历 (jiǎntǐ) covers BOTH traditional 曆 (calendar) AND 歷 (history / experience). 历史 (lìshǐ, history — written 歷史 in traditional script), 日历 (rìlì, calendar — written 日曆 traditional), 阳历 (yánglì, solar calendar), 农历 (nónglì, "agricultural calendar" = lunar calendar). For learners moving between traditional and simplified scripts, the 历 = 歷 + 曆 merge is essential to track.

Japanese on-reading レキ (reki) — 西暦 (seireki, Western calendar / Gregorian dating — used as the standard reference in Japanese alongside the traditional era system 元号), 還暦 (kanreki, 60th birthday — major Japanese life milestone celebrated with red clothing, since the person symbolically "returns to childhood" by completing the sexagenary cycle). Kun-reading こよみ (koyomi) — 暦 (koyomi, calendar) — used poetically. 旧暦 (kyūreki, old / lunar calendar) and 新暦 (shinreki, new / solar calendar) are common in Japanese seasonal references.

Memory aid: orderly grain (厤) plus sun (日) — recording the sun's succession = calendar. Three different scripts: Korea 曆, Japan 暦, Mainland 历.