I don't know what the official Duolingo policy is on words like "i går", "i kväll", "i morgon" etc., but as a native Swedish speaker I am so used to writing "igår, ikväll, imorgon" that I didn't even stop and think about it. According to Språkrådet, both forms are acceptable but writing the words apart are recommended. I suppose that is the original, older form, which is becoming less and less used in modern Swedish.
Our official policy is to write them apart, but it's universally accepted not to in the cases of "i går", "i dag" and the like.
Dear Emil,if we translate,,,hela dagen,,,of course you accept that,,,the whole day,,,is right but why using,,,the whole day yesterday or,,,the whole yesterday are wrong
Exactly! I never write them apart, since that is not what I was taught at school. But the new recommendation is to split them for consistency with "i sommar", "i onsdags" etc.
My translation "Yesterday it snowed the whole day" was wrong according to the program. Why? (My own language is Swedish, not English)
Antagligen pga ordföljden. Om alla kombinationer vore tillåtna, så skulle det innebära väldigt mycket arbete för kursskaparna :). De måste ju lägga till alla korrekta översättningar explicit.