時を表す in・on・at：朝・曜日・7時

01at: points on the clock

Use at for precise points: clock times, mealtimes treated as points, and festival moments. At 7 o'clock, at noon, at midnight, at night, at Christmas — each one answers the question exactly when. Think of at as a pin dropped on the timeline.

02on: days and dates

Use on for days of the week and calendar dates: on Monday, on May 1st, on Christmas Day. When a date includes the day, on wins — on Monday morning, on the weekend (American) — because the day is the anchor. If you can circle it on a calendar page, reach for on.

03in: longer stretches

Use in for months, seasons, years, and parts of the day: in July, in summer, in 2026, in the morning. These are containers of time rather than points — you are somewhere inside the period. Centuries and decades follow the same logic: in the 1990s.

Watch the famous pair: arrive on time means punctual, while arrive in time means early enough to do something — in time for dinner, in time to help. And drop the preposition entirely before this, last, next, every, yesterday, and tomorrow: see you next Monday, not on next Monday.

04Try a week of your life

Write seven lines about your week using all three: at 7:30, on Tuesday, in the evening. Then add one deadline with by — finish this by Friday — and notice how by means no later than, not at that moment. Keeping your own examples next to each other makes the small-to-big picture stick.

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