Date picker accessibility

Keyboard interaction

Key	Action
`Digits`	Type into the segment. It moves on once no other digit could follow.
`Up and down arrows`	Step the segment; Page Up and Page Down step further.
`Left and right arrows, Tab`	Previous or next segment.
`Backspace`	Clear the segment, then go back one.
`A and P`	Set AM or PM.

A field is a group: name it with aria-label or aria-labelledby. Each segment is a spinbutton named for its part, which reads months by name and empty segments as “Empty”.
Segments are editable text, so touch keyboards open on digits.
The picker’s button is named “Choose a date”, and its popover is a dialog. Picking a date returns focus to the button.
The calendar inside works as the calendar does.