..............Prepositions often confused............

On, At, In. (Time)

On.

！Don't say: My uncle will arrive at Saturday.

√ Say: My uncle will arrive on Saturday.

At.

！ Don't say: I usually get up on seven o'clock.

√ Say: I usually get up at seven o'clock.

In.

！ Don't say: She goes for a walk at the afternoon.

√ Say: She goes for a walk in the afternoon.

(1). Use "on" with the days of the week or month:on Friday, on March 25, on New Year's Day.

(2). Use "at" with the exact time: at four o'clock, at dawn, at noon, at sunset, at midnight.

(3). Use"in" with a period of time: in April, in winter, in 1945, in the morning.

Also: at night and by day.