Okay, mea culpa on one point. You did, indeed, give us a link to where you got datepicker.js from.
But when I go look at that page
http://www.htmldrive.net/edit_media/2010/201009/20100902/Date%20Time%20Picker/datepicker.htm and do a VIEW==>>SOURCE indeed I see all those libraries, just as you showed them.
So...you need them.
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A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.