The date field has always been mandatory as far back as I can remember.

If you feel very strongly about it, you can switch the field to "freeform" mode (with the buttons next to it) and enter whatever gibberish you please.

The documentation for https://commons.wikimedia.org/wiki/Template:Information also states that the date is required.

If its mandatory, what do you expect people to do if they dont know the answer?

In T115318#1721533, @Bawolff wrote:

If its mandatory, what do you expect people to do if they dont know the answer?

{{unknown|date}}. Should be added as an option, or a help text.

In T115318#1721533, @Bawolff wrote:

If its mandatory, what do you expect people to do if they dont know the answer?

I think a truly completely unknown date is pretty rare. In the vast majority of cases, you can at least specify a year, a decade or something similar. There are lots of options for this, and a template that covers most of them: {{Other date}}.

In T115318#1721472, @matmarex wrote:

The documentation for https://commons.wikimedia.org/wiki/Template:Information also states that the date is required.

It also says "If the creation date of a file (not moved from other project) is unknown, {{Upload date}} can be used". This is what UploadWizard should be doing, if it really wants to follow the documentation. (Or it could simply avoid forcing a requirement which doesn't exist; that was my original suggestion.)

FWIW: I think {{upload date}} would be a good compromise if the user doesn't fill out the form, and ignores a warning (similar to empty categories field) that says "hey you should really do this, it makes life easier".