At, in. At refers to a point of time; In to a larger space of time.
1. He cam at 8 o’clock in the morning.
2. Similarly, for a small place we use “at”, e.g.
He lives at Kuala Lumpur in Malaysia.
The university is at Petaling Jaya in Kuala Lumpur.
Please attend my class to learn the techniques of memorizing and usage. Call Bryan @ 012-664-1376.