“Welchen Tag haben wir heute” and “Welchen Datum haben wir heute”

I saw these two sentences today.

One thing I noticed is that “n” is added to "Welche".

Please explain why we do that.
 

“Welchen Tag haben wir heute”
I would say that Wenchen Tag  is the masculine accusative form of welcher.
https://www.verbformen.com/declension/articles/welcher.htm

However I would have expected the second phrase to be:
“Welches Datum haben wir heute”  Are you sure ​“Welchen Datum haben wir heute” is correct?

Maybe Leah can explain.
 

Hallo RexV und sfpugh!

You're right, sfpugh: welchen is the masculine accusative form of welcher, which is why it's used here in the example of Welchen Tag haben wir heute? Literally, this translates to "Which day do we have today?"

For the second example, it should indeed be welches, since Datum is neuter - Welches Datum haben wir heute?

I hope that this clears everything up!

Tschüss,

Liss