The calendar picks a day, a range of days, or several days. Values are plain ISO dates, such as 2026-09-25, with no time zone to shift them, so they go straight to a server or an <input type="date">.
Weeks start on the locale’s first day, and names and digits follow its language. min, max and unavailable rule out days, months shows several side by side, and the title zooms out to months and years for distant dates.
Every day is reachable from the keyboard, as in the WAI-ARIA date picker, and each is named by its full date.
A delivery day
Days before today, after max or ruled out by unavailable can’t be picked, but the keyboard still passes through them.
A range
With selection="range", the first pick starts the range and the band follows the pointer until the second. months="2" and weekNumbers show more at once.
Several days
With selection="multiple", each pick adds or removes a day. firstDay starts the week on another day than the locale’s.