These three prepositions are used to describe when, what date or day, or what time something happens.
The preposition in is used to describe what happens during years, centuries, months, and other periods of time.
The preposition on is used to describe an action that occurs on specific dates or days or days of the week.
The preposition at is used to describe precise times of day.
Note (1) The prepositions in, on and at generally follow the order of largest to smallest, in terms of time, regardless of their order in the sentence.
I was born in February 1986, on a Tuesday, at 6 p.m.
I was born on a Tuesday at 6 p.m., in February 1986.
I was born at 6 p.m. on a Tuesday, in February 1986.
Note (2) In general a preposition is not used with last, next, every, or this.
This Tuesday, I’ll call my doctor. Next summer, I plan to go to Cuba.
These three prepositions are used to describe the length or duration of an action, or the non-specific period of time (that is, not a date or time, but an interval or phase) of an occurrence.
The preposition for is used to indicate how long someone or something has done something, or how long something has been happening or has existed.
The preposition while is used with a verb form to represent the length of time of an action, or two actions occurring at the same time. The length of the action is not important.
Note: While can also be used as a conjunction, similar in meaning to although.
While I like your project, it still needs some revisions.
The preposition during is used with a noun to represent the period of time in which an action occurs.
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