關於英文at、 on 、in 的區別。?

All of at, on, in can be used as, apart from some other usages, preposition of time, place and location with some definite rules, minor exceptions aside. All grammar books would have a chapter to show the differentiation.

Just a few examples:
Time:
at - (Hours) at 3 o'clock, at noon, at midnight
on - (Days) on Friday, on May 5, 2017, on my birthday, on weekend
in - (bigger time span) in two weeks, in a month, in June, in 2016, in the 90's, in 21st century

Location:
at - (an address or specific location) at the supermarket
on - (street)
in - (district, city, country) in Hollywood, in New York, in Canada

Place:
at - (for a point) at the bus stop, at the entrance
on - (for a surface) on the wall, on the floor
in - (for an enclosed space) in my pocket, in a car, in a building