Its not strange in english dear, but its going to be very nice if we can view all the alternatives of any answer here in duolingo.. sadly there is no option for that.
And for this sentence in particular,, english have many ways to express it in equivalence.
Hopefully we will have such option in duolingo later on >.
"Ocak bir hafta sonra." Translation: January is in a week.
"Ocak bir hafta sonra." Translation: January is in a week or January is a week away. Both correct English translations. Duo or somebody agrees with me after posting this answer six hours later.
(I had a short rest before continuing learning)
If you talk about a specific point like Christmas, a meeting, a soccer game or anything like that use -den/dan suffix.
If you talk about a time duration like a month, two years, ten minutes, one hour and so on, don't use -den/dan suffix.
Don't confuse time points and time durations. Compare them
Üç saat sonra - After three hours / Three hours later
Saat üçten sonra - After three o'clock
Bir ay sonra - After a month / A month later
Ocak'tan sonra - After January
İki hafta sonra -> After two weeks / Two weeks later
İki haftadan sonra -> After the two weeks (which were mentioned before)
I asked that one earlier:
sonra + Ablative (dAn. etc.) after x-time
sonra +Nominative after x-time from now on
Since we don't have January every other week here it must be the second case (Nom.) If you are talking about seeds you put in the ground, which sprout after two weeks whenever you plant them it should be Ablative.
I hope I got it right.
The "r" sound in Turkish has the tongue approach the roof of the mouth but not quite touch. Especially when "r" comes at the end of a word the tongue gets so close that the air coming over it makes a hissing sound like an "sh," and the vocal cords stop moving at the word's end, so it's harder to hear it as being a "r" sound.