The three prepositions used to describe time are “at,” “on,” and “in.”

  1. “At” is used for three things:
    1. times expressed with numbers, as on a clock
    2. the words noon, midnight, and night
    3. expressions like “the current time,” “the present,” and “the moment.
  2. “On” is used with:
    1. specific dates
    2. days of the week
    3. the expressions “weekends,” “the weekend,” and “weekdays”
  3. “In” is used with:
    1. some times of day (morning, afternoon, evening, night)
    2. the phrases “the past,” “the present,” and “the future”
    3. and a/an quantities of time with a/an (a minute, an hour, a day, a week, a month, a year)

In a typical sentence in English, a prepositional phrase of place comes before a prepositional phrase of time. Prepositional phrases can be placed before the subject in a sentence, or after the verb phrase.