Why is the accusative form of "den" used here? Or is this just a conventional collocation that I should just keep in mind?
Time expressions without prepositions use accusative case. With prepositions they use dative case. It's explained here :)
How would you say "We have all day to play"?
Wir haben den ganzen Tag zum Spielen.
zum is a contraction of "zu dem". The verb "spielen" is used as a noun and thus has to be capitalized.
Why not: "We were playing" ?
If you add "all day" it should be ok.
With "all day" :) Wasn't ok. Thought there was a rule or something. Didn't accept continuous on several occasions
"We were playing all day" is an accepted translation.
why is "we played ((the))) whole day" rejected
isnt den equal to the???
"We played the whole day" is an accepted translation.
what if we use alle?
"Alle" only works with plural nouns. (Unlike all in English)
Acutally, in German "all" can also be used for uncountable (mass) nouns in singular.
All meine Liebe - all my love
is "all the day" wrong? if so, why?
It sounds, at best, archaic to me.
'We have played the whole day' Should be accepted, surely?
Can one also say "Wir haben den gesamten Tag gespielt"? Or is "gesamten" only used for concrete objects like "Der gesamte Kopf ist rot"?
It‘s ok, but „ganzen” is more idiomatic.
Gesamt is more like “complete”.