Expected: pick a new value in each control, then Submit. The page reloads with the
values in the query string, in the control's canonical form — the colour as
%23rrggbb, the date kinds as their ISO strings: for instance
?colour=%23663399&date=2026-09-15&time=10%3A35&when=2026-09-15T10%3A35&month=2026-09&week=2026-W38&empty=.
A picker that was cancelled contributes the value it had before it opened.
Reset puts every control back to its value attribute, undoing
whatever the pickers chose. A control left empty submits as name=; a
disabled one is left out of the query string entirely.