The most popular bootstrap date picker is currently: https://github.com/eternicode/bootstrap-datepicker
(thanks to @dentarg for digging it up)
A simple instantiation only requires:
HTML
<input class="datepicker">
Javascript
$('.datepicker').datepicker();
See a simple example here https://jsfiddle.net/k6qsm5no/1/ or the full docs here http://bootstrap-datepicker.readthedocs.org/en/latest/