Is it in the evening or at the evening?

In the evening. Or some say "of an evening"

"In the evening"

Both are correct; however, the more concise and therefore more elegant usage is "by evening."

After 6:00 pm

We do not know when Jesus was born. Until the fourth century, December 25th was celebrated as the birthday of the god Mithras. Emperor Constantine chose to celebrate the birthday of Jesus on the same...