What time is it?

Morning:
5 a.m. to 11:59 a.m.
It is 8 a.m. It's the morning.

Afternoon:
12 p.m. to 5:59 p.m.
It is 1 p.m. It's the afternoon.

Evening:
6 p.m. to 8:59 p.m.
It is 7 p.m. It's the evening.

Night:
9 p.m. to 4:59 a.m.
It is 11 p.m. It's night.

You talk about times of the day. You say:

in the morning

I read letters in the morning.

in the evening

They write emails in the evening.

in the afternoon

She writes in the afternoon.

at night

We read at night.