Event.addBehavior({
  'select#event_date_1i, select#event_date_2i, select#event_date_3i, select#event_date_4i, select#event_date_5i' : function() {
		var old_start_date = new Date(
			$F('event_date_1i'),
			$F('event_date_2i')-1,
			$F('event_date_3i'),
			$F('event_date_4i'),
			$F('event_date_5i'));
	
		Event.observe(this, 'change', function() {
			// Do the calculations
			new_start_date = new Date($F('event_date_1i'),$F('event_date_2i')-1,$F('event_date_3i'),$F('event_date_4i'),$F('event_date_5i'));
			old_end_date = new Date($F('event_end_date_1i'),$F('event_end_date_2i')-1,$F('event_end_date_3i'),$F('event_end_date_4i'),$F('event_end_date_5i'));
			delta = new_start_date - old_start_date;
			new_end_date = new Date();
			new_end_date.setTime(old_end_date.getTime() + delta );
			// console.log('Old start date',old_start_date);	
			// console.log('New start date',new_start_date);
			// console.log('Delta',delta)
			// console.log('Old end date',old_end_date);
			// console.log('New end date',new_end_date);
			
			old_start_date = new_start_date;

			// And update the display
			$('event_end_date_1i').setValue(new_end_date.getFullYear());
			$('event_end_date_2i').setValue(new_end_date.getMonth() + 1);
			$('event_end_date_3i').setValue(new_end_date.getDate());	
			$('event_end_date_4i').setValue(new_end_date.getHours());
			$('event_end_date_5i').setValue(new_end_date.getMinutes());
			
			// check_end_date = new Date($F('event_end_date_1i'),$F('event_end_date_2i')-1,$F('event_end_date_3i'),$F('event_end_date_4i'),$F('event_end_date_5i'));
			// console.log('Date x-check. Desired:',new_end_date,' Actual:',check_end_date);
		});
	}
});