def test_formatTimeWithDefaultFormat(self):
        """
        Default time stamp format is RFC 3339 and offset respects the timezone
        as set by the standard C{TZ} environment variable and L{tzset} API.
        """
        if tzset is None:
            raise SkipTest(
                "Platform cannot change timezone; unable to verify offsets."
            )

        def testForTimeZone(name, expectedDST, expectedSTD):
            setTZ(name)

            localDST = mktime((2006, 6, 30, 0, 0, 0, 4, 181, 1))
            localSTD = mktime((2007, 1, 31, 0, 0, 0, 2, 31, 0))

            self.assertEqual(formatTime(localDST), expectedDST)
            self.assertEqual(formatTime(localSTD), expectedSTD)

        # UTC
        testForTimeZone(
            "UTC+00",
            u"2006-06-30T00:00:00+0000",
            u"2007-01-31T00:00:00+0000",
        )

        # West of UTC
        testForTimeZone(
            "EST+05EDT,M4.1.0,M10.5.0",
            u"2006-06-30T00:00:00-0400",
            u"2007-01-31T00:00:00-0500",
        )

        # East of UTC
        testForTimeZone(
            "CEST-01CEDT,M4.1.0,M10.5.0",
            u"2006-06-30T00:00:00+0200",
            u"2007-01-31T00:00:00+0100",
        )

        # No DST
        testForTimeZone(
            "CST+06",
            u"2006-06-30T00:00:00-0600",
            u"2007-01-31T00:00:00-0600",
        )

        Default time stamp format is RFC 3339 and offset respects the timezone
        as set by the standard C{TZ} environment variable and L{tzset} API.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_format.py