Talked to my sister in Tanzania and she says they count by "solar time" sunrise is approximately 6am, so 7 is hour one. Still trying to figure out where the lesson referenced below is but that's the basic.
Given the Swahili includes the word dakika, I'd say the minutes should be included in the English. There are plenty of sentences where variations should be accepted (but usually aren't). I don't think this is one of them.