Example:

This is an input with calendar bound , so you can use it to change dates using calendar widget.

The look of the calendar elements is defined using CSS file calendar.css.
The functioanlity is done using JavaScript file calendar.js, which defines global variable calendar, which is used to trigger calendar's functionalities like toggle, hide, etc.
When calendar is showed the following keys handlers are bound:

Esc - exit calendar,
Arrow left - go to previous month,
Arrow right - go to next month.

Supported locales are "en" (English) and "pl" (Polish).
To handle a new locale one needs to define additional attributes in the following local JavaScript variables:

WEEK_DAYS_LABELS
MONTH_NAMES_LABELS
FORMATTERS
UNFORMATTERS

The example code of existing handlers can be easily reused.

If you have none of above set as default in your browser and the document's <html> element has no lang attribute defined current browser's locale settings will try to be used. If not valid/supported/found the default taken will be en.

Change of a CSS file can ease the process of changing the look and feel completely: