Found more of Sputnik's date helper funcs.

test/harness/Date_library.js

 // Copyright 2009 the Sputnik authors.  All rights reserved.
 // This code is governed by the BSD license found in the LICENSE file.
 
+//the following values are normally generated by the sputnik.py driver
+var $LocalTZ,
+    $DST_start_month,
+    $DST_start_sunday,
+    $DST_start_hour,
+    $DST_start_minutes,
+    $DST_end_month,
+    $DST_end_sunday,
+    $DST_end_hour,
+    $DST_end_minutes;
+
+(function () {
+    /**
+      * Finds the first date, starting from |start|, where |predicate|
+      * holds.
+      */
+    var findNearestDateBefore = function(start, predicate) {
+        var current = start;
+        var month = 1000 * 60 * 60 * 24 * 30;
+        for (var step = month; step > 0; step = Math.floor(step / 3)) {
+            if (!predicate(current)) {
+                while (!predicate(current))
+                    current = new Date(current.getTime() + step);
+                    current = new Date(current.getTime() - step);
+                }
+        }
+        while (!predicate(current)) {
+            current = new Date(current.getTime() + 1);
+        }
+        return current;
+    }
+
+    var juneDate = new Date(2000, 6, 20, 0, 0, 0, 0);
+    var decemberDate = new Date(2000, 12, 20, 0, 0, 0, 0);
+    var juneOffset = juneDate.getTimezoneOffset();
+    var decemberOffset = decemberDate.getTimezoneOffset();
+    var isSouthernHemisphere = (juneOffset > decemberOffset);
+    var winterTime = isSouthernHemisphere ? juneDate : decemberDate;
+    var summerTime = isSouthernHemisphere ? decemberDate : juneDate;
+    
+    $LocalTZ = new Date().getTimezoneOffset() / -60;
+    
+    
+    var dstStart = findNearestDateBefore(winterTime, function (date) {
+        return date.getTimezoneOffset() == summerTime.getTimezoneOffset();
+    });
+    $DST_start_month = dstStart.getMonth();
+    $DST_start_sunday = dstStart.getDate() > 15 ? '"last"' : '"first"';
+    $DST_start_hour = dstStart.getHours();
+    $DST_start_minutes = dstStart.getMinutes();
+      
+    var dstEnd = findNearestDateBefore(summerTime, function (date) {
+        return date.getTimezoneOffset() == winterTime.getTimezoneOffset();
+    });
+    $DST_end_month = dstEnd.getMonth();
+    $DST_end_sunday = dstEnd.getDate() > 15 ? '"last"' : '"first"';
+    $DST_end_hour = dstEnd.getHours();
+    $DST_end_minutes = dstEnd.getMinutes();
+    
+    return;
+})();
+
+
 //15.9.1.2 Day Number and Time within Day
 function Day(t) {
   return Math.floor(t/msPerDay);
@@ -323,19 +386,4 @@ function ConstructDate(year, month, date, hours, minutes, seconds, ms){
   var r11 = MakeDate(r9, r10);
   
   return TimeClip(UTC(r11));
-}
-
+}
\ No newline at end of file
-
-//the following values are normally generated by the sputnik.py driver
-// for now, we'll just use 0 for everything
-/*
-var $LocalTZ=-8;
-var $DST_start_month=2;
-var $DST_start_sunday='first';
-var $DST_start_hour=2;
-var $DST_start_minutes=0;
-var $DST_end_month=10;
-var $DST_end_sunday='first';
-var $DST_end_hour=2;
-var $DST_end_minutes=0;
-*/