Afternoon, evening & night

1) afternoon and evening

In most people's speech, afternoon starts after lunch and changes to
evening after work (or after normal working hours).

2) evening and night

Evening changes to night more or less at bedtime. But note that

Good evening usually has the sense of 'Hello' and Good night of 'Goodbye' -

Good night is not used to greet people.

A: Good evening. Terrible weather, isn't it?

B: Yes, dreadful.

A: Hasn't stopped raining forweeks. Well, Imustbe going. Goodnight.

B: Goodnight.