One point in time
On is used with days:
At is used with noon, night, midnight, and with the time of day:
- I will see you on Monday.7
- The week begins on Sunday.
In is used with other parts of the day, with months, with years, with seasons:
- My plane leaves at noon.
- The movie starts at 6 p.m.
- He likes to read in the afternoon.
- The days are long in August.
- The book was published in 1999.
- The flowers will bloom in spring.
To express extended time, English uses the following prepositions: since, for, by, from—to, from-until, during,(with)in
- She has been gone since yesterday. (She left yesterday and has not returned.)
- I'm going to Paris for two weeks. (I will spend two weeks there.)
- The movie showed from August to October. (Beginning in August and ending in October.)
- The decorations were up from spring until fall. (Beginning in spring and ending in fall.)
- I watch TV during the evening. (For some period of time in the evening.)
- We must finish the project within a year. (No longer than a year.)
Student or Learner