| at | clock times, night, midday, Christmas, Easter | at 9:30 / at night |
| on | days, dates and a day with its part of the day | on Monday morning / on 5 May |
| in | months, seasons, years, morning, afternoon, evening | in January / in summer |
| Length | the period gets longer from at to on to in | at 7 o'clock / on Monday / in July |
| No preposition | before this, next, last, every, today, tomorrow | I'm busy this week. / I walk every morning. |
| Trap | dates take on, months take in | My birthday is on 5 May. / It's cold in January. |
| Trap | the weekend takes at | We relax at the weekend. (US: on the weekend) |