SO fiddle

Test Fiddle mainly for SO Questions

by Nick Craver

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/overcast/jquery-ui.css">
<div>
<p>Date: <input type="text" class="datepicker" id="dp1"></p>
</div>
<div>
<p>Date: <input type="text" class="datepicker" id="dp2"></p>
</div>

CSS

div { padding: 10px; }

JavaScript

var pickable = { dp1: [1, 4], dp2: [2, 5] };
$('.datepicker').each(function() {
  $(this).datepicker({
    beforeShowDay: function(date){ 
        var day = date.getDay(), days = pickable[this.id];
        return [$.inArray(day, days) > -1, ""];
    }
  });
});