Given:
Where the id = datepicker tells the javascript to attach all the datepicker code to
Simple!! Use clientidmode="static" in your input text control.
clientidmode="static"
Example- input runat="server" id="datepicker" type="text" clientidmode="Static"
input runat="server" id="datepicker" type="text" clientidmode="Static"
This should solve your problem.