diff --git a/ui/ui.datepicker.js b/ui/ui.datepicker.js
index 82a3016d9..3e01a6ae0 100644
--- a/ui/ui.datepicker.js
+++ b/ui/ui.datepicker.js
@@ -250,8 +250,8 @@ $.extend(Datepicker.prototype, {
 
 		this._pos = (pos ? (pos.length ? pos : [pos.pageX, pos.pageY]) : null);
 		if (!this._pos) {
-			var browserWidth = window.innerWidth || document.documentElement.clientWidth ||	document.body.clientWidth;
-			var browserHeight = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight;
+			var browserWidth = document.documentElement.clientWidth;
+			var browserHeight = document.documentElement.clientHeight;
 			var scrollX = document.documentElement.scrollLeft || document.body.scrollLeft;
 			var scrollY = document.documentElement.scrollTop || document.body.scrollTop;
 			this._pos = // should use actual width/height below
@@ -633,8 +633,8 @@ $.extend(Datepicker.prototype, {
 		var dpHeight = inst.dpDiv.outerHeight();
 		var inputWidth = inst.input ? inst.input.outerWidth() : 0;
 		var inputHeight = inst.input ? inst.input.outerHeight() : 0;
-		var viewWidth = (window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth) + $(document).scrollLeft();
-		var viewHeight = (window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight) + $(document).scrollTop();
+		var viewWidth = document.documentElement.clientWidth + $(document).scrollLeft();
+		var viewHeight = document.documentElement.clientHeight + $(document).scrollTop();
 
 		offset.left -= (this._get(inst, 'isRTL') ? (dpWidth - inputWidth) : 0);
 		offset.left -= (isFixed && offset.left == inst.input.offset().left) ? $(document).scrollLeft() : 0;