In, on, At

In:
Month - my birthday is in February.

Year - the Titanic sank in 1912.

Season - I'll come India in summer.

Time period - she will be in 10 minutes.

On:
Days - I will meet you on Monday.

Dates - her birthday is on 27th April 2018.

At: specific time
The school starts at 9'o clock.

I had my lunch at noon.

I was waiting at Egmore station in Chennai on Monday.