"That is a Saturday."

Translation: Das ist ein Samstag.

[Lee374561]

"Students, there will be a test on April tenth."
"Oh, wait... that is a Saturday."

Sounds perfectly fine to me.

[Craig136066]

Native speakers - sagt jemand "Sonnabend"?

[mizinamo]

Native speakers - sagt jemand "Sonnabend"?

Yes. Especially in the north.

[Craig136066]

Danke sehr!

[Laila182399]

What even is this sentence

[MortiBiRD]

A possible scenario.

L: "Die Prüfung findet am 01.07.2017 statt."

S1: "Hey S2, was für ein Tag ist der 01.07?"

S2: "Das ist ein Samstag."

You'll encounter more often an answer like "Der 01.07 ist ein Samstag" (Its male, because 01.07 is connected to "der Tag" and Tag is grammatical male).

[rednh]

Warum nicht 'Sonnabend'?

[mizinamo]

Warum nicht 'Sonnabend'?

That's a northern German regionalism. Samstag is the standard word.

[Craig136066]

Agreed, but that doesn't make it incorrect.

[mizinamo]

that doesn't make it incorrect.

There are accepted translations that include the word Sonnabend.

In general, though, the course does not accept regionalisms.