What We Fixed
Firefox does not support the datetime-local input type, so the time portion of any date/time field — on the Calendar create modal, task modals, and appointment modals — was silently missing for Firefox users. Dates could be entered but the time was inaccessible, meaning tasks and appointments were always saved without a time component.
We replaced the single datetime-local input with separate date and time inputs that are supported by all major browsers. The behaviour is otherwise identical: selecting a date and time in one field still produces a combined value, and clearing the field works as before.
Fields affected: Calendar event date/time, task due date/time, and appointment date/time.