I've read the entire thread and honestly, I think we all need to respect other people's ways of doing things even if it doesn't agree with ours. You want to learn somebody's language, you have to play by their rules. If you don't, you are short changing yourself. If they say Saa tatu is means the 3rd hour I.e 9 o'clock, Then so be it! In the end you want to communicate with them and you can't go to Tanzania and set up a meeting for 9am saying "Saa tisa Asubuhi"... At best they'll show up at 3pm (which is actually Saa tisa Usiku if I'm right)... In the end, it's your loss.
This system of hours is what was used in medieval Europe (you can still see it in the daily services in monastic rules) and the Roman world. I assume Swahili got it through early Islam.
The bottom line is Duolingo is a poor platform for teaching the cultural background of how time is told. Were it not for others students, I too would just keep plugging away not understanding why my answers were wrong.
If you go on the website there is grammar and notes sections with the lesson, it is explained there :) For some reason it's just not available in the app.
Really good advice - never base on google translator, especialy about kiswahili. Only good dictionaries. And - JamesT.Wilson - you still repeat the same. Is it such a dificult what I said ? =D