Should I say 午後 once, twice or something else?

Question

Class is from 6 to 8 pm.

授業は午後六時から午後八時までです

授業は午後六時から八時までです

How should this be expressed ?

Answer 1

Saying 午後 twice is not wrong at all, but 授業は午後6時から8時までです is enough.

If you want to say the class lasts until the next morning, you can add 午前, 朝 or 翌【よく】 (="on the next day"). e.g., "授業は午後6時から翌8時までです"

Answer 2

To further avoid confusion, you can just use 24H time. It is quite common in Japan.

• 授業は18時から20時までです

I've also seen izakaya/karaoke places/other nighttime entertainment establishments that go past 24 to indicate how late they are open.

(居酒屋) 閉店：26時