Common time-telling slips
Ten minutes on the topic's own four common mistakes: два paired with singular је instead of су, пет paired with plural су instead of је, an accusative time expression left in the 2–4 form сата instead of сати, and the fixed question phrase reaching for the bare сат instead of сати. Build sentences around postponing a meeting, catching each slip in turn, before the unit's own listening and reading put the whole topic to work.
The part of the grammar page this lesson drills — read it here, then use it.
Telling the hour
The count noun сат follows the same 1 / 2–4 / 5+ pattern as numbers-a1 - see the exact forms and verbs in the table below.
That је/су switch is the one detail worth memorizing on purpose: 2–4 pairs with plural су, while 1 and 5+ both pair with singular је - an asymmetry that has nothing to do with real-world plurality.
Minutes, half and quarter hours
Minutes past the hour are added with и (and): пет и десет (5:10), пет и петнаест or пет и четврт (5:15, четврт = quarter).
Пола (half) needs care: пола шест means 5:30, not 6:30 - it points at the UPCOMING hour, literally half [of the way to] six. Четврт до (quarter to) works the same way: четврт до шест means 5:45.
Special cases
To say at a time, use у + accusative: Долазим у пет сати. (I'm arriving at five o'clock.) The question form is a fixed phrase: У колико сати долазиш? (What time are you arriving?).
Подне (noon) and поноћ (midnight) are fixed words on their own, not a number + сат: Сада је подне. (It's noon now.) Formal schedules (trains, TV listings) commonly switch to the 24-hour clock, e.g. у 17 и 30.