Confused Prepositions

On, At, and In (time factor)

Rule: on is used with the days of the week or month (on Sunday, on February 15, etc.); at is used to denote the exact time (at dawn, at 10 o’clock, etc.); and in is used with a period of time (in spring, in the evening, etc.).

Incorrect Usage: (a) The delegates will arrive at Monday.

  (b) He goes to bed on 11 o’clock.

  (c) My mother goes for a walk at the evening.                                

Correct Usage:    (a) The delegates will arrive on Monday.

                                (b) He goes to bed at 11 o’clock.

                                (c) My mother goes for a walk in the evening.