I was born in April.
He goes to the park on Saturdays.
She wakes up at 7:00.
We use 'in' for months and years, 'on' for days and dates, and 'at' for times.
in January / July / 2014
on Monday / Friday / May 1st
at 11:30 / 4 o’clock / half past two
We can use ‘on’ for special days and ‘at’ for special times too.
on my birthday / New Year’s Day / the last day of school
at midnight / bedtime / dinner time
We say... We don’t say...
I had lots of fun on my birthday. (NOT I had lots of fun in my birthday.)
We don’t watch TV at dinner time. (NOT We don’t watch TV on dinner time.)