時間の in / on / at In, On, At: Telling Time
前置詞 Prepositions
ズームで覚えます。at は時刻(点)、on は曜日・日付(カレンダーの1マス)、in は月・年・季節(大きな箱)。at 7 → on Monday → in July。ズームアウトするほど at → on → in です。
Think zoom levels. At pins a clock time (a point), on covers a day (a calendar tile), in holds months, years, and seasons (a big box). At 7 → on Monday → in July — the wider the span, the bigger the word.
点・マス・箱
Point, Tile, Box
at 7:00 は時計の針が指す一点。on Monday はカレンダーの1マス。in July はマスが31個入った大きな箱です。この3段ズームで、時間の前置詞はほとんど片づきます。細かい例外はありますが、まず本体を体に入れてから拾えば十分です。
At 7:00 is the point the clock hand touches. On Monday is one calendar tile. In July is the big box holding thirty-one tiles. This three-step zoom settles most cases. There are exceptions — but learn the system first and mop them up later.
3段ズーム The three zoom levels
The meeting starts at 10.
会議は10時に始まる。
時刻=点。 Clock time — a point.
See you on Friday.
金曜に会おう。
曜日=マス。日付も on(on May 5th)。 A day is a tile — dates too: on May 5th.
It gets cold in December.
12月は寒くなる。
月=箱。年・季節も in(in 2026 / in winter)。 Months are boxes — so are years and seasons: in 2026, in winter.
in the morning
ふつうの「朝に」は箱の in。 The ordinary "in the morning" is the box.
I run in the morning.
朝は走ることにしている。
on the morning of ...
特定の日の朝は、その日のマス扱いで on。 A particular day's morning becomes that day's tile — on.
We left on the morning of the 5th.
5日の朝に出発した。
よくある間違い Common Mistake
I was born in May 5th.
5月5日生まれです。(のつもりで)
I was born on May 5th.
5月5日生まれです。
月だけなら in May(箱)。日付が付いた瞬間、カレンダーの1マスになるので on May 5th です。
Month alone: in May — the box. Add the date and it shrinks to a tile: on May 5th.
- at night 夜に 夜だけ「点」扱いの伝統。理屈より歴史の組。 Night gets point treatment by tradition — history, not logic.
- in time 間に合って 締め切りという箱の「中に」滑り込む、余裕のイメージ。 Sliding inside the box before it closes — with room to spare.
- on time 時間どおりに 定刻という1点の「上に」ぴったり乗る。in time との違いはここ。 Landing exactly on the appointed point. That's the whole contrast with in time.
- at the last minute 土壇場で 「最後の1分」まで研ぎ澄まされた点。 The final minute, sharpened to a point.
まとめ Summary
- at =時刻の点、on =曜日・日付のマス、in =月・年・季節の箱。 At = clock points; on = day tiles; in = month, year, season boxes.
- 日付が付いたら on(on May 5th)。 Dates take on: on May 5th.
- 週末は米 on / 英 at。どちらも正解。 Weekend: on (US) / at (UK) — both right.
- in time =間に合う、on time =定刻ぴったり。 In time = early enough; on time = exactly on the dot.