diff --git a/strftime.js b/strftime.js
index c05c3f0..37635ab 100644
--- a/strftime.js
+++ b/strftime.js
@@ -595,10 +595,8 @@
             else
                 weekday--;
         }
-
-        var firstDayOfYearUtc = Date.UTC(date.getFullYear(), 0, 1),
-            dateUtc = Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()),
-            yday = Math.floor((dateUtc - firstDayOfYearUtc) / 86400000),
+        var firstDayOfYear = new Date(date.getFullYear(), 0, 1),
+            yday = (date - firstDayOfYear) / 86400000,
             weekNum = (yday + 7 - weekday) / 7;
 
         return Math.floor(weekNum);
diff --git a/test.js b/test.js
index 5b6fd62..0b0a974 100755
--- a/test.js
+++ b/test.js
@@ -115,9 +115,6 @@ assert.format('%z', null, '+0000');
 assert.format('%:z', null, '+00:00');
 assert.format('%%', '%'); // any other char
 assert.format('%F %T', null, '1970-01-01 00:00:00', new Date(0));
-assert.format('%U', '13', "12", (new Date('03-26-2017 00:00:00')));
-assert.format('%U', '13', null, (new Date('03-27-2017 00:00:00')));
-assert.format('%U', '14', "13", (new Date('04-02-2017 00:00:00')));
 ok('GMT');