De or het diplomadag?

The correct Dutch article is:

de diplomadag

This word is not in the word lists we use to double-check answers.

How to use diplomadag

the diplomadagde diplomadag
this diplomadagdeze diplomadag
that diplomadagdie diplomadag
our diplomadagonze diplomadag
your diplomadagjouw diplomadag
every diplomadagelke diplomadag
which diplomadag?welke diplomadag?
a big diplomadag / the big diplomadageen grote diplomadag, de grote diplomadag