Just good old-fashioned plain HTML. Keyboard accessible by default.
Tab navigates forward; shift+TAB goes back.
Arrow keys make magic happen!
Built-in validation
Pattern recognition: <input pattern="(\d{5}([\-]\d{4})?)">
Hit space, then arrow keys allow you to choose dates. Enter selects the option. Esc dismisses the datepicker. Or just type in a date.
Like the date picker–but for times!
Space bar to toggle a checkbox on or off.
Arrow to cycle between radio buttons.
Use arrow keys to increase/ decrease by 10. (Or just type a number!)
Enter first letter of option you want (e.g. "F" for France, then arrow up/down).