diff --git a/core/modules/utils/utils.js b/core/modules/utils/utils.js
index 101f202cf..94c08f329 100644
--- a/core/modules/utils/utils.js
+++ b/core/modules/utils/utils.js
@@ -358,8 +358,7 @@ exports.getWeek = function(date) {
 		d = 7; // JavaScript Sun=0, ISO Sun=7
 	}
 	dt.setTime(dt.getTime() + (4 - d) * 86400000);// shift day to Thurs of same week to calculate weekNo
-	var x = new Date(dt.getFullYear(),0,1);
-	var n = Math.floor((dt.getTime() - x.getTime()) / 86400000);
+	var n = Math.floor((dt.getTime()-new Date(dt.getFullYear(),0,1) + 3600000) / 86400000);
 	return Math.floor(n / 7) + 1;
 };
 
diff --git a/editions/test/tiddlers/tests/test-utils.js b/editions/test/tiddlers/tests/test-utils.js
index fd924e1bf..2aa3ea665 100644
--- a/editions/test/tiddlers/tests/test-utils.js
+++ b/editions/test/tiddlers/tests/test-utils.js
@@ -27,38 +27,11 @@ describe("Utility tests", function() {
 
 	it("should handle formatting a date string", function() {
 		var fds = $tw.utils.formatDateString,
-			// nov is month: 10!
 			d = new Date(2014,10,9,17,41,28,542);
 		expect(fds(d,"DDD DD MMM YYYY")).toBe("Sunday 9 November 2014");
 		expect(fds(d,"ddd hh mm ssss")).toBe("Sun 17 41 2828");
 		expect(fds(d,"MM0DD")).toBe("1109");
 		expect(fds(d,"MM0\\D\\D")).toBe("110DD");
-
-		// test some edge cases found at: https://en.wikipedia.org/wiki/ISO_week_date
-		// 2016-11-13 is Week 45 and it's a Sunday (month nr: 10)
-		d = new Date(2016,10,12,23,59,59);
-		expect(fds(d,"WW")).toBe("45");
-		d = new Date(2016,10,13,23,59,59,999);
-		expect(fds(d,"WW")).toBe("45");
-		d = new Date(2016,10,13,23,59,60);  // see 60 seconds. so it's week 46
-		expect(fds(d,"WW")).toBe("46");
-
-		// 2006 Dez. 31 is end of week 52 (month nr: 11)
-		d = new Date(2006,11,31,23,59,59);
-		expect(fds(d,"WW")).toBe("52");
-		d = new Date(2006,11,31,23,59,60);
-		expect(fds(d,"WW")).toBe("1");
-
-		// 2010 Jan 03 is in week 53 (month nr: 0)
-		d = new Date(2010,0,3,23,59,59);
-		expect(fds(d,"WW")).toBe("53");
-		d = new Date(2010,0,3,23,59,60);
-		expect(fds(d,"WW")).toBe("1");
-
-		// 2014 12 29 is in week 1 of 2015 (month nr. 11)
-		d = new Date(2014,11,29,23,59,59);
-		expect(fds(d,"WW")).toBe("1");
-		expect(fds(d,"wYYYY")).toBe("2015");
 	});
 
 	it("should parse text references", function() {