Make test suite timezone-independent.

And to enforce this, run all the tests in a fixed, unusual time zone from
now on.

test/run-tests.py

@@ -993,6 +993,19 @@ def init():
 
         sys.stdout.write(colorize("b", "## Testing PhantomJS "+ver[0])+"\n")
 
+    # Run all the tests in Chatham Islands Standard Time, UTC+12:45.
+    # This timezone is deliberately chosen to be unusual: it's not a
+    # whole number of hours offset from UTC *and* it's more than twelve
+    # hours offset from UTC.
+    #
+    # The Chatham Islands do observe daylight savings, but we don't
+    # implement that because testsuite issues only reproducible on two
+    # particular days out of the year are too much tsuris.
+    #
+    # Note that the offset in a TZ value is the negative of the way it's
+    # usually written, e.g. UTC+1 would be xxx-1:00.
+    os.environ["TZ"] = "CIST-12:45:00"
+
     return runner
 
 def main():

test/standards/javascript/date.js

@@ -1,8 +1,8 @@
 test(function() {
     var date = new Date('2012-09-07');
     assert_not_equals(date.toString(), 'Invalid Date');
-    assert_equals(date.getDate(), 6);
-    assert_equals(date.getMonth(), 8);
+    assert_equals(date.getUTCDate(), 7);
+    assert_equals(date.getUTCMonth(), 8);
     assert_equals(date.getYear(), 112);
 }, "new Date()");