It is pretty hard to find a simple-yet-functional and good looking datepicker script.

The most popular one is probably the jQuery UI's picker but it is heavy in size for any project that actually does only need a datepicker.

Pikaday - JavaScript Datepicker

Pikaday is a standalone JavaScript datapicker which is small in size (<5kb) and can work well with Moment.js if advanced formatting is needed.

The design of the picker can be easily customized with CSS (the default style already looks good) and offers "quick year switching".

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