"Því seinna þennan sama daga" - What grammatical case is 'daga'?
Example sentence: "Því seinna þennan sama daga reyndi mamma að drepa sig með því að stökkva fram af bílastæðahúsi á Hverfisgötunni".
What grammatical case are these words in "þennan sama daga"?
I would expect this sentence to say "þennan sama dag" in the accusative singular without the final -a. "Daga" is either accusative or genitive plural.
Thank you in advance.