The basic time kanji
Japanese time expressions use three key kanji: 時 (ji — hour/o'clock), 分 (fun/pun — minute), 秒 (byou — second). These attach to numbers: 三時 (3 o'clock), 十五分 (15 minutes), 三十秒 (30 seconds). The system is perfectly regular once you know the number kanji.
To tell the time: [hour] 時 [minute] 分. 午後三時半 (gogo sanji han — 3:30 PM). 午前 (gozen) means AM (literally "before noon"); 午後 (gogo) means PM (literally "after noon").
Asking and answering about time
何時ですか (nanji desu ka) — What time is it? 今何時？(ima nanji?) — What time is it now? (casual). 〜時に (-ji ni) — at [time]: 三時に (at 3 o'clock). 〜時間 (-jikan — hours of duration): 三時間 (for three hours, a duration rather than a clock time). The distinction between 時 (clock time) and 時間 (duration) is important and trips up many learners.
半 (han — half) is used for the half-hour: 三時半 is 3:30. For 15 minutes (quarter past), Japanese uses 十五分: 三時十五分 (3:15). There is no equivalent of "quarter to" — Japanese always states the exact minute count: 三時四十五分 (3:45), not "quarter to four."
Time-related expressions
Common time vocabulary: 今 (ima — now), 後で (atode — later), さっき (sakki — a moment ago), 毎日 (mainichi — every day), 来週 (raishuu — next week), 先月 (sengetsu — last month), もうすぐ (mousugu — very soon). The kanji 時 also appears in words like 時間 (time/duration), 時代 (era/period), 時刻 (appointed time), making it one of the most versatile kanji in daily Japanese.
Learn the Japanese scripts
Reading Japanese time requires knowing hiragana and numbers.