O'Clock
suffix
If there's a number before 時, it means o'clock. For example １時 is 1:00, and ２３時 is 23:00 or 11pm.
じ
The reading is the same as the one you learned with the kanji.
三時になったらおやつ休けいにしましょう。
When it’s three o’clock let’s have our afternoon snack break.
コウイチの家の台どころで二時半にまちあわせね。
Let's meet up at Koichi's kitchen at 2:30, ok?
いつも１５時にワニカニのレビューをするんですか？
Do you usually do your WaniKani reviews at 3pm?