JavaScript Datepicker deletes inputs default value

[Jolly Boy]

I'm using boostrap datepicker (I think), it works fine and dandy.

-jquery loads date into input when page loads
-datepicker modal shows on click to input
-problem: if the modal shows and the user doesnt click a date (clicks something else), the original date in the input is deleted.

                    $('#period_end').datepicker({
                        format: 'yyyy-mm-dd',
                        autoclose : true,
                        todayHighlight : true
                    });