Common prepositions of time fall into 3 categories:

AT is Used for Precise Times

School finishes at 1 o'clock.

I wake up at 5.30am, every day.

The sky is beautiful at sunrise.

At Christmas I like to buy a lot of presents for my family.

We came here at the same time.

At night we like to stay in the garden.

IN is Used for Months, Years, Centuries, or Longer Periods of Time

My dad’s birthday is in December.

He was born in 1972.

It's always hard to wake up early in the morning.

ON is Used for Days and Dates

For example:

We play football on Sundays.

We are going on holiday on the 25th July.