All interactive elements of your page should be accessible by keyboard (e.g. text boxes, buttons, etc). That means you should be able focus on them via
Shift+Tab keys. Focused via keyboard elements have their own visual state. For example, you can focus
date-input component below via
Tab, then call
Enter and select date, using left-right keys,
Shift+Tab to focus year and month,
Enter to confirm the selection and
Esc to close the picker.