"It takes one year."
I was thinking the same thing, but according to this site, the -kan suffix is optional for years. It's only required for hours and weeks (and months are their own thing). https://www.learn-japanese-adventure.com/japanese-numbers-durations.html
It's discouraging that users were commenting on this issue 6 MONTHS AGO and it's still an issue for me today.
I understand that this beta is new, and perhaps you're gauging its popularity before you go in and fix things. However, issues like this decrease the popularity of this software, and I've encountered numerous other issues--unnatural or archaic phrases, fill-in-the-blank questions where the necessary sentence parts are missing, etc. In these cases, it's not even possible for me to report an error because an appropriate error message option isn't provided.
I took 2 years of Japanese about 10 years ago and studied abroad, so I'm using Duo primarily as a review tool, but god help anyone using this tool to actually LEARN the language in any organic, lasting way.
For example: Without some explanatory context, it's impossible for users to notice that kiru, haku, and kaburu all mean "to wear," but depend on where the clothing goes on the body.
Similarly, lessons aren't arranged in a scaffolded way so that they focus on skills--the use of a particular particle, for instance. Users are left to their own devices to figure out how the hell these things function (or left to hash it out on the discussion boards, which are filled with misinformation.)
I know this is a free product and resources are limited, but I've heard that the other language programs are quite good. I only hope that Japanese eventually receives the same care and attention from your engineers and instructional designers.