Talk? Even people in the same culture say things differently - 9:15 or quarter past nine, for example. But more importantly, look at any european plane, bus or train schedule, store/office/restaurant/museum opening hours signage, or street parking signs to see the importance of the 24 hour clock.
If you used "toward" as your translation of the word "verso" in this sentence, and Duo marked it wrong, then you should report it, as long as there were no other issues with the translation. According to Collins and wordreference.com, "toward" is a solid definition for the sense of "verso"
It doesn't really matter what time format is used around the world. This sentence should be translated using literal (but grammatically correct) translation as a lot of us are not native English speakers, how could we guess if the translation is using US or British or whatever time.
When using the 24 hour time system the colon is not used. Numerical digits are not accepted on Duolingo either. Not totally sure how the site wants this translated: into American time - 3 o'clock, or how they would say it verbally in Europe - they write it 1500 h. In the military this is said fifteen hundred hours. It seems the best way to go is to use the words for numbers and translate it to North American time.
Actually, you're wrong. I know this because I have been living in Europe for the past 2.5 years, but more credibly, the Wikipedia page for "24-hour clock" says this:
"The most commonly used separator symbol between hours, minutes and seconds is the colon, which is also the symbol used in ISO 8601. In the past, some European countries used the dot on the line as a separator, but most national standards on time notation have since then been changed to the international standard colon. In some contexts (e.g., U.S. military, some computer protocols), no separator is used (e.g., 2359)."
"Military time" is different from the world standard 24-hour clock. And numerical digits have definitely been accepted on Duolingo in the past, though I haven't been on much for the past 2 months, so perhaps that has been recently changed.
Edit: Here's the Wikipedia link. https://en.wikipedia.org/wiki/24-hour_clock
It is an american app and thinks in american! Thats why it doesnt accept if you write 15. In the us they have no idea what it is. Its like metrical system...works all over the world but it isnt suitable for them. Duo should accept 15 because brittish english is used and teached ewerywhere!! I am nervous!
Seems like a lot of people are having trouble with the 24 hour clock. Very simply if a number is less than 12 it is a.m. and anything more than 12 is p.m. You just count how many more than twelve and you will have your p.m. hour. For example: 15:00 is three more than twelve so its 3pm, 1900 is seven more than twelve so its 7pm and so on. Hope this helps.
I understand that numbers are not accepted, but why not if you write 'fifteen'? English language is so wide spread that I don't see why it should be so tightly connected to the English culture. I live in Finland, where we use officially 24h time, in spoken language both. But here I can say also in English "I will do it by 15" and everyone will understand.