Calendar

Date picking — inline in a booking page, or inside a Popover as a date field.

Days are 32px squares on a 2px grid; the popup padding drops to 8px when it contains a Calendar.
Inline for a booking surface where the dates are the page; in a Popover behind an outline Button for a date field.
The trigger label shows the selected date, not the word “Pick a date”, once a value exists.