Some code to manipulate the jQuery UI calendar.

date-picker.js

$(document).ready(function(){
	
		var today = new Date();
		today = new Date(today.getFullYear(), today.getMonth(), today.getDate()); // Zero time components
		var tomorrow = today.getDay() + 1;
		var next_two_days = today.getDay() + 2;
		var next_three_days = today.getDay() + 3;
		var curr_time = getTime();
		var curr_day = today.getDate();
		
		$(".datepicker").datepicker({
			numberOfMonths: 1,
			showButtonPanel: true,
			showOn: 'button',
			buttonImage: '/themes/public/basic/images/calendar.png',
			buttonImageOnly: true,
			dateFormat: 'yy-mm-dd',
			beforeShowDay: function(date) {
			        var day = date.getDay();
			        if(curr_time > '5:00 PM')
					{
						return [(day != 0  && day != tomorrow && day != next_two_days && day != next_three_days  && date.getDate() >= curr_day), ''];
			    	}
					else
					{
						return [(day != 0  && day != tomorrow && day != next_two_days && date.getDate() >= curr_day), ''];
					}
				}
		});

		function getTime() {
			var dTime = new Date();
			var hours = dTime.getHours();
 			var minute = dTime.getMinutes();
			var period = "AM";
			if (hours > 12)
			{
 				period = "PM"
			}
			else
			{
				period = "AM";
			}
 			
			hours = ((hours > 12) ? hours - 12 : hours)
			return hours + ":" + minute + " " + period
		}
	
});