def test_pickling(self):
        "Test reversibility of pickling."
        import pickle

        date = Datetime360Day(year=1,
                              month=2,
                              day=3,
                              hour=4,
                              minute=5,
                              second=6,
                              microsecond=7)
        self.assertEqual(date, pickle.loads(pickle.dumps(date)))
    def setUp(self):
        self.date1_365_day = DatetimeNoLeap(-5000, 1, 2, 12)
        self.date2_365_day = DatetimeNoLeap(-5000, 1, 3, 12)
        self.date3_gregorian = DatetimeGregorian(1969,  7, 20, 12)

        # last day of the Julian calendar in the mixed Julian/Gregorian calendar
        self.date4_gregorian = DatetimeGregorian(1582, 10, 4)
        # first day of the Gregorian calendar in the mixed Julian/Gregorian calendar
        self.date5_gregorian = DatetimeGregorian(1582, 10, 15)

        self.date6_proleptic_gregorian = DatetimeProlepticGregorian(1582, 10, 15)

        self.date7_360_day = Datetime360Day(2000, 1, 1)

        self.date8_julian = DatetimeJulian(1582, 10, 4)

        # a datetime.datetime instance (proleptic Gregorian calendar)
        self.datetime_date1 = datetime(1969,  7, 21, 12)

        self.delta = timedelta(hours=25)
    def test_sub(self):
        # subtracting a timedelta
        previous_day = self.date1_365_day - self.delta
        self.assertEqual(previous_day.day, self.date1_365_day.day - 1)

        def total_seconds(td):
            """Equivalent to td.total_seconds() on Python >= 2.7. See
            https://docs.python.org/2/library/datetime.html#datetime.timedelta.total_seconds
            """
            return (td.microseconds +
                    (td.seconds + td.days * 24 * 3600) * 10**6) / 10**6

        # sutracting two netcdftime.datetime instances
        delta = self.date2_365_day - self.date1_365_day
        # date1 and date2 are exactly one day apart
        self.assertEqual(total_seconds(delta), 86400)

        # subtracting netcdftime.datetime from datetime.datetime
        delta = self.datetime_date1 - self.date3_gregorian
        # real_date2 and real_date1 are exactly one day apart
        self.assertEqual(total_seconds(delta), 86400)

        # subtracting datetime.datetime from netcdftime.datetime
        delta = self.date3_gregorian - self.datetime_date1
        # real_date2 and real_date1 are exactly one day apart
        self.assertEqual(total_seconds(delta), -86400)

        # Test the Julian/Gregorian transition.
        self.assertEqual(self.date5_gregorian - self.delta,
                         DatetimeGregorian(1582, 10, 3, 23))

        # The proleptic Gregorian calendar does not have invalid dates.
        self.assertEqual(self.date6_proleptic_gregorian - self.delta,
                         DatetimeProlepticGregorian(1582, 10, 13, 23))

        # The Gregorian calendar has no year zero.
        self.assertEqual(
            DatetimeGregorian(1, 1, 1) - self.delta,
            DatetimeGregorian(-1, 12, 30, 23))

        # The 360_day calendar has year zero.

        self.assertEqual(self.date7_360_day - timedelta(days=2000 * 360),
                         Datetime360Day(0, 1, 1))

        # Test going over the year boundary.
        self.assertEqual(
            DatetimeGregorian(2000, 3, 1) - timedelta(days=29 + 31 + 31),
            DatetimeGregorian(1999, 12, 1))

        # Year 2000 is a leap year.
        self.assertEqual(
            DatetimeGregorian(2000, 3, 1) - self.delta,
            DatetimeGregorian(2000, 2, 28, 23))

        def invalid_sub_1():
            self.date1_365_day - 1

        def invalid_sub_2():
            1 - self.date1_365_day

        def invalid_sub_3():
            self.date1_365_day - self.datetime_date1

        def invalid_sub_4():
            self.datetime_date1 - self.date1_365_day

        def invalid_sub_5():
            self.date3_gregorian - self.date1_365_day

        for func in [invalid_sub_1, invalid_sub_2]:
            self.assertRaises(TypeError, func)

        for func in [invalid_sub_3, invalid_sub_4, invalid_sub_5]:
            self.assertRaises(ValueError, func)
    def runTest(self):
        """testing netcdftime"""
        # test mixed julian/gregorian calendar
        # check attributes.
        self.assertTrue(self.cdftime_mixed.units == 'hours')
        self.assertTrue(
            str(self.cdftime_mixed.origin) == '   1-01-01 00:00:00')
        self.assertTrue(self.cdftime_mixed.unit_string ==
                        'hours since 0001-01-01 00:00:00')
        self.assertTrue(self.cdftime_mixed.calendar == 'standard')
        # check date2num method. (date before switch)
        d = datetime(1582, 10, 4, 23)
        t1 = self.cdftime_mixed.date2num(d)
        assert_almost_equal(t1, 13865687.0)
        # check num2date method.
        d2 = self.cdftime_mixed.num2date(t1)
        self.assertTrue(str(d) == str(d2))
        # this is a non-existant date, should raise ValueError.
        d = datetime(1582, 10, 5, 0)
        self.assertRaises(ValueError, self.cdftime_mixed.date2num, d)
        # check date2num/num2date with date after switch.
        d = datetime(1582, 10, 15, 0)
        t2 = self.cdftime_mixed.date2num(d)
        assert_almost_equal(t2, 13865688.0)
        d2 = self.cdftime_mixed.num2date(t2)
        self.assertTrue(str(d) == str(d2))
        # check day of year.
        ndayr = d.timetuple()[7]
        self.assertTrue(ndayr == 288)
        # test using numpy arrays.
        t = numpy.arange(t2, t2 + 240.0, 12.)
        t = numpy.reshape(t, (4, 5))
        d = self.cdftime_mixed.num2date(t)
        self.assertTrue(d.shape == t.shape)
        d_check = "1582-10-15 00:00:001582-10-15 12:00:001582-10-16 00:00:001582-10-16 12:00:001582-10-17 00:00:001582-10-17 12:00:001582-10-18 00:00:001582-10-18 12:00:001582-10-19 00:00:001582-10-19 12:00:001582-10-20 00:00:001582-10-20 12:00:001582-10-21 00:00:001582-10-21 12:00:001582-10-22 00:00:001582-10-22 12:00:001582-10-23 00:00:001582-10-23 12:00:001582-10-24 00:00:001582-10-24 12:00:00"
        d2 = [str(dd) for dd in d.flat]
        self.assertTrue(d_check == ''.join(d2))
        # test julian calendar with numpy arrays
        d = self.cdftime_julian.num2date(t)
        self.assertTrue(d.shape == t.shape)
        d_check = "1582-10-05 00:00:001582-10-05 12:00:001582-10-06 00:00:001582-10-06 12:00:001582-10-07 00:00:001582-10-07 12:00:001582-10-08 00:00:001582-10-08 12:00:001582-10-09 00:00:001582-10-09 12:00:001582-10-10 00:00:001582-10-10 12:00:001582-10-11 00:00:001582-10-11 12:00:001582-10-12 00:00:001582-10-12 12:00:001582-10-13 00:00:001582-10-13 12:00:001582-10-14 00:00:001582-10-14 12:00:00"
        d2 = [str(dd) for dd in d.flat]
        self.assertTrue(d_check == ''.join(d2))
        # test proleptic gregorian calendar.
        self.assertTrue(self.cdftime_pg.units == 'seconds')
        self.assertTrue(str(self.cdftime_pg.origin) == '   1-01-01 00:00:00')
        self.assertTrue(
            self.cdftime_pg.unit_string == 'seconds since 0001-01-01 00:00:00')
        self.assertTrue(self.cdftime_pg.calendar == 'proleptic_gregorian')
        # check date2num method.
        d = datetime(1990, 5, 5, 2, 17)
        t1 = numpy.around(self.cdftime_pg.date2num(d))
        self.assertTrue(t1 == 62777470620.0)
        # check num2date method.
        d2 = self.cdftime_pg.num2date(t1)
        self.assertTrue(str(d) == str(d2))
        # check day of year.
        ndayr = d.timetuple()[7]
        self.assertTrue(ndayr == 125)
        # check noleap calendar.
        # this is a non-existant date, should raise ValueError.
        self.assertRaises(ValueError,
                          utime,
                          'days since 1600-02-29 00:00:00',
                          calendar='noleap')
        self.assertTrue(self.cdftime_noleap.units == 'days')
        self.assertTrue(
            str(self.cdftime_noleap.origin) == '1600-02-28 00:00:00')
        self.assertTrue(self.cdftime_noleap.unit_string ==
                        'days since 1600-02-28 00:00:00')
        self.assertTrue(self.cdftime_noleap.calendar == 'noleap')
        assert_almost_equal(
            self.cdftime_noleap.date2num(self.cdftime_noleap.origin), 0.0)
        # check date2num method.
        d1 = datetime(2000, 2, 28)
        d2 = datetime(1600, 2, 28)
        t1 = self.cdftime_noleap.date2num(d1)
        t2 = self.cdftime_noleap.date2num(d2)
        assert_almost_equal(t1, 400 * 365.)
        assert_almost_equal(t2, 0.)
        t12 = self.cdftime_noleap.date2num([d1, d2])
        assert_almost_equal(t12, [400 * 365., 0])
        # check num2date method.
        d2 = self.cdftime_noleap.num2date(t1)
        self.assertTrue(str(d1) == str(d2))
        # check day of year.
        ndayr = d2.timetuple()[7]
        self.assertTrue(ndayr == 59)
        # non-existant date, should raise ValueError.
        date = datetime(2000, 2, 29)
        self.assertRaises(ValueError, self.cdftime_noleap.date2num, date)
        # check all_leap calendar.
        self.assertTrue(self.cdftime_leap.units == 'days')
        self.assertTrue(str(self.cdftime_leap.origin) == '1600-02-29 00:00:00')
        self.assertTrue(
            self.cdftime_leap.unit_string == 'days since 1600-02-29 00:00:00')
        self.assertTrue(self.cdftime_leap.calendar == 'all_leap')
        assert_almost_equal(
            self.cdftime_leap.date2num(self.cdftime_leap.origin), 0.0)
        # check date2num method.
        d1 = datetime(2000, 2, 29)
        d2 = datetime(1600, 2, 29)
        t1 = self.cdftime_leap.date2num(d1)
        t2 = self.cdftime_leap.date2num(d2)
        assert_almost_equal(t1, 400 * 366.)
        assert_almost_equal(t2, 0.)
        # check num2date method.
        d2 = self.cdftime_leap.num2date(t1)
        self.assertTrue(str(d1) == str(d2))
        # check day of year.
        ndayr = d2.timetuple()[7]
        self.assertTrue(ndayr == 60)
        # double check date2num,num2date methods.
        d = datetime(2000, 12, 31)
        t1 = self.cdftime_mixed.date2num(d)
        d2 = self.cdftime_mixed.num2date(t1)
        self.assertTrue(str(d) == str(d2))
        ndayr = d2.timetuple()[7]
        self.assertTrue(ndayr == 366)
        # check 360_day calendar.
        self.assertTrue(self.cdftime_360day.units == 'days')
        self.assertTrue(
            str(self.cdftime_360day.origin) == '1600-02-30 00:00:00')
        self.assertTrue(self.cdftime_360day.unit_string ==
                        'days since 1600-02-30 00:00:00')
        self.assertTrue(self.cdftime_360day.calendar == '360_day')
        assert_almost_equal(
            self.cdftime_360day.date2num(self.cdftime_360day.origin), 0.0)
        # check date2num,num2date methods.
        # use datetime from netcdftime, since this date doesn't
        # exist in "normal" calendars.
        d = datetimex(2000, 2, 30)
        t1 = self.cdftime_360day.date2num(d)
        assert_almost_equal(t1, 360 * 400.)
        d2 = self.cdftime_360day.num2date(t1)
        assert_equal(str(d), str(d2))
        # check day of year.
        d = datetime(2001, 12, 30)
        t = self.cdftime_360day.date2num(d)
        assert_almost_equal(t, 144660.0)
        date = self.cdftime_360day.num2date(t)
        self.assertTrue(str(d) == str(date))
        ndayr = date.timetuple()[7]
        self.assertTrue(ndayr == 360)
        # Check fraction
        d = datetime(1969, 12, 30, 12)
        t = self.cdftime_360day.date2num(d)
        date = self.cdftime_360day.num2date(t)
        assert_equal(str(d), str(date))
        # test proleptic julian calendar.
        d = datetime(1858, 11, 17, 12)
        t = self.cdftime_jul.date2num(d)
        assert_almost_equal(t, 7528932.0)
        d1 = datetime(1582, 10, 4, 23)
        d2 = datetime(1582, 10, 15, 0)
        assert_almost_equal(
            self.cdftime_jul.date2num(d1) + 241.0,
            self.cdftime_jul.date2num(d2))
        date = self.cdftime_jul.num2date(t)
        self.assertTrue(str(d) == str(date))
        # test julian day from date, date from julian day
        d = datetime(1858, 11, 17)
        mjd = JulianDayFromDate(d)
        assert_almost_equal(mjd, 2400000.5)
        date = DateFromJulianDay(mjd)
        self.assertTrue(str(date) == str(d))
        # test iso 8601 units string
        d = datetime(1970, 1, 1, 1)
        t = self.cdftime_iso.date2num(d)
        assert_equal(numpy.around(t), 3600)
        # test fix for issue 75 (seconds hit 60 at end of month,
        # day goes out of range).
        t = 733499.0
        d = num2date(t, units='days since 0001-01-01 00:00:00')
        dateformat = '%Y-%m-%d %H:%M:%S'
        assert_equal(d.strftime(dateformat), '2009-04-01 00:00:00')
        # test edge case of issue 75 for numerical problems
        for t in (733498.999, 733498.9999, 733498.99999, 733498.999999,
                  733498.9999999):
            d = num2date(t, units='days since 0001-01-01 00:00:00')
            t2 = date2num(d, units='days since 0001-01-01 00:00:00')
            assert (abs(t2 - t) < 1e-5)  # values should be less than second
        # Check equality testing
        d1 = datetimex(1979, 6, 21, 9, 23, 12)
        d2 = datetime(1979, 6, 21, 9, 23, 12)
        assert (d1 == d2)
        # check timezone offset
        d = datetime(2012, 2, 29, 15)
        # mixed_tz is -6 hours from UTC, mixed is UTC so
        # difference in elapsed time is -6 hours.
        assert (self.cdftime_mixed_tz.date2num(d) -
                self.cdftime_mixed.date2num(d) == -6)

        # Check comparisons with Python datetime types

        # Note that d1 has to use the proleptic Gregorian calendar to
        # be comparable to d2: datetime.datetime uses the proleptic
        # Gregorian calendar and year 1000 is before the
        # Julian/Gregorian transition (1582-10-15).
        d1 = num2date(0, 'days since 1000-01-01', 'proleptic_gregorian')

        d2 = datetime(2000, 1, 1)

        # The date d3 is well after the Julian/Gregorian transition
        # and so this Gregorian date can be compared to the proleptic
        # Gregorian date d2.
        d3 = num2date(0, 'days since 3000-01-01', 'standard')
        assert d1 < d2
        assert d2 < d3

        # check all comparisons
        assert d1 != d2
        assert d1 <= d2
        assert d2 > d1
        assert d2 >= d1

        # check datetime hash
        d1 = datetimex(1995, 1, 1)
        d2 = datetime(1995, 1, 1)
        d3 = datetimex(2001, 2, 30)
        assert hash(d1) == hash(d1)
        assert hash(d1) == hash(d2)
        assert hash(d1) != hash(d3)
        assert hash(d3) == hash(d3)

        # check datetime immutability
        # using assertRaises as a context manager
        # only works with python >= 2.7 (issue #497).
        immutability_tests = {
            "year": 1999,
            "month": 6,
            "day": 5,
            "hour": 10,
            "minute": 33,
            "second": 45,
            "dayofwk": 1,
            "dayofyr": 52,
            "format": '%Y'
        }

        for name, value in immutability_tests.items():
            self.assertRaises(AttributeError, setattr, d1, name, value)

        # Check leading white space
        self.assertEqual(str(self.cdftime_leading_space.origin),
                         ' 850-01-01 00:00:00')

        #issue 330
        units = "seconds since 1970-01-01T00:00:00Z"
        t = utime(units)
        for n in range(10):
            assert n == int(round(t.date2num(t.num2date(n))))

        #issue 344
        units = 'hours since 2013-12-12T12:00:00'
        assert (1.0 == date2num(num2date(1.0, units), units))

        # test rountrip accuracy
        # also tests error found in issue #349
        calendars=['standard', 'gregorian', 'proleptic_gregorian', 'noleap', 'julian',\
                   'all_leap', '365_day', '366_day', '360_day']
        dateformat = '%Y-%m-%d %H:%M:%S'
        dateref = datetime(2015, 2, 28, 12)
        ntimes = 1001
        for calendar in calendars:
            eps = 100.
            units = 'microseconds since 1800-01-30 01:01:01'
            microsecs1 = date2num(dateref, units, calendar=calendar)
            for n in range(ntimes):
                microsecs1 += 1.
                date1 = num2date(microsecs1, units, calendar=calendar)
                microsecs2 = date2num(date1, units, calendar=calendar)
                date2 = num2date(microsecs2, units, calendar=calendar)
                err = numpy.abs(microsecs1 - microsecs2)
                assert (err < eps)
                assert (
                    date1.strftime(dateformat) == date2.strftime(dateformat))
            units = 'milliseconds since 1800-01-30 01:01:01'
            eps = 0.1
            millisecs1 = date2num(dateref, units, calendar=calendar)
            for n in range(ntimes):
                millisecs1 += 0.001
                date1 = num2date(millisecs1, units, calendar=calendar)
                millisecs2 = date2num(date1, units, calendar=calendar)
                date2 = num2date(millisecs2, units, calendar=calendar)
                err = numpy.abs(millisecs1 - millisecs2)
                assert (err < eps)
                assert (
                    date1.strftime(dateformat) == date2.strftime(dateformat))
            eps = 1.e-4
            units = 'seconds since 0001-01-30 01:01:01'
            secs1 = date2num(dateref, units, calendar=calendar)
            for n in range(ntimes):
                secs1 += 0.1
                date1 = num2date(secs1, units, calendar=calendar)
                secs2 = date2num(date1, units, calendar=calendar)
                date2 = num2date(secs2, units, calendar=calendar)
                err = numpy.abs(secs1 - secs2)
                assert (err < eps)
                assert (
                    date1.strftime(dateformat) == date2.strftime(dateformat))
            eps = 1.e-5
            units = 'minutes since 0001-01-30 01:01:01'
            mins1 = date2num(dateref, units, calendar=calendar)
            for n in range(ntimes):
                mins1 += 0.01
                date1 = num2date(mins1, units, calendar=calendar)
                mins2 = date2num(date1, units, calendar=calendar)
                date2 = num2date(mins2, units, calendar=calendar)
                err = numpy.abs(mins1 - mins2)
                assert (err < eps)
                assert (
                    date1.strftime(dateformat) == date2.strftime(dateformat))
            eps = 1.e-5
            units = 'hours since 0001-01-30 01:01:01'
            hrs1 = date2num(dateref, units, calendar=calendar)
            for n in range(ntimes):
                hrs1 += 0.001
                date1 = num2date(hrs1, units, calendar=calendar)
                hrs2 = date2num(date1, units, calendar=calendar)
                date2 = num2date(hrs2, units, calendar=calendar)
                err = numpy.abs(hrs1 - hrs2)
                assert (err < eps)
                assert (
                    date1.strftime(dateformat) == date2.strftime(dateformat))
            eps = 1.e-5
            units = 'days since 0001-01-30 01:01:01'
            days1 = date2num(dateref, units, calendar=calendar)
            for n in range(ntimes):
                days1 += 0.00001
                date1 = num2date(days1, units, calendar=calendar)
                days2 = date2num(date1, units, calendar=calendar)
                date2 = num2date(days2, units, calendar=calendar)
                err = numpy.abs(days1 - days2)
                assert (err < eps)
                assert (
                    date1.strftime(dateformat) == date2.strftime(dateformat))

        # issue 353
        assert (num2date(0, 'hours since 2000-01-01 0') == datetime(
            2000, 1, 1, 0))

        # issue 354
        num1 = numpy.array([[0, 1], [2, 3]])
        num2 = numpy.array([[0, 1], [2, 3]])
        dates1 = num2date(num1, 'days since 0001-01-01')
        dates2 = num2date(num2, 'days since 2001-01-01')
        assert (dates1.shape == (2, 2))
        assert (dates2.shape == (2, 2))
        num1b = date2num(dates1, 'days since 0001-01-01')
        num2b = date2num(dates2, 'days since 2001-01-01')
        assert (num1b.shape == (2, 2))
        assert (num2b.shape == (2, 2))
        assert_almost_equal(num1, num1b)
        assert_almost_equal(num2, num2b)

        # issue 357 (make sure time zone offset in units done correctly)
        # Denver time, 7 hours behind UTC
        units = 'hours since 1682-10-15 -07:00 UTC'
        # date after gregorian switch, python datetime used
        date = datetime(1682, 10, 15)  # assumed UTC
        num = date2num(date, units)
        # UTC is 7 hours ahead of units, so num should be -7
        assert (num == -7)
        assert (num2date(num, units) == date)
        units = 'hours since 1482-10-15 -07:00 UTC'
        # date before gregorian switch, netcdftime datetime used
        date = datetime(1482, 10, 15)
        num = date2num(date, units)
        date2 = num2date(num, units)
        assert (num == -7)
        assert (date2.year == date.year)
        assert (date2.month == date.month)
        assert (date2.day == date.day)
        assert (date2.hour == date.hour)
        assert (date2.minute == date.minute)
        assert (date2.second == date.second)

        # issue 362: case insensitive calendars
        self.assertTrue(self.cdftime_mixed_capcal.calendar == 'standard')
        self.assertTrue(self.cdftime_noleap_capcal.calendar == 'noleap')
        d = datetime(2015, 3, 4, 12, 18, 30)
        units = 'days since 0001-01-01'
        for cap_cal, low_cal in (('STANDARD', 'standard'), ('NoLeap',
                                                            'noleap'),
                                 ('Gregorian', 'gregorian'), ('ALL_LEAP',
                                                              'all_leap')):
            d1 = date2num(d, units, cap_cal)
            d2 = date2num(d, units, low_cal)
            self.assertEqual(d1, d2)
            self.assertEqual(num2date(d1, units, cap_cal),
                             num2date(d1, units, low_cal))
        # issue 415
        t = datetimex(2001, 12, 1, 2, 3, 4)
        self.assertEqual(t, copy.deepcopy(t))

        # issue 442
        units = "days since 0000-01-01 00:00:00"
        # this should fail (year zero not allowed with real-world calendars)
        try:
            date2num(datetime(1, 1, 1), units, calendar='standard')
        except ValueError:
            pass
        # this should not fail (year zero allowed in 'fake' calendars)
        t = date2num(datetime(1, 1, 1), units, calendar='360_day')
        self.assertEqual(t, 360)
        d = num2date(t, units, calendar='360_day')
        self.assertEqual(d, Datetime360Day(1, 1, 1))
        d = num2date(0, units, calendar='360_day')
        self.assertEqual(d, Datetime360Day(0, 1, 1))

        # list around missing dates in Gregorian calendar
        # scalar
        units = 'days since 0001-01-01 12:00:00'
        t1 = date2num(datetime(1582, 10, 4), units, calendar='gregorian')
        t2 = date2num(datetime(1582, 10, 15), units, calendar='gregorian')
        self.assertEqual(t1 + 1, t2)
        # list
        t1, t2 = date2num([datetime(1582, 10, 4),
                           datetime(1582, 10, 15)],
                          units,
                          calendar='gregorian')
        self.assertEqual(t1 + 1, t2)
        t1, t2 = date2num([datetime(1582, 10, 4),
                           datetime(1582, 10, 15)],
                          units,
                          calendar='standard')
        self.assertEqual(t1 + 1, t2)
        # this should fail: days missing in Gregorian calendar
        try:
            t1, t2, t3 = date2num([
                datetime(1582, 10, 4),
                datetime(1582, 10, 10),
                datetime(1582, 10, 15)
            ],
                                  units,
                                  calendar='standard')
        except ValueError:
            pass
        # test fix for issue #596 - julian day calculations wrong for negative years,
        # caused incorrect rountrip num2date(date2num(date)) roundtrip for dates with year
        # < 0.
        u = utime("seconds since 1-1-1", calendar='julian')
        date1 = datetimex(-1, 1, 1)
        date2 = u.num2date(u.date2num(date1))
        assert (date2.year == date1.year)
        assert (date2.month == date1.month)
        assert (date2.day == date1.day)
        assert (date2.hour == date1.hour)
        assert (date2.minute == date1.minute)
        assert (date2.second == date1.second)
        assert_almost_equal(JulianDayFromDate(date1), 1721057.5)
        # issue 596 - negative years fail in utime.num2date
        u = utime("seconds since 1-1-1", "proleptic_gregorian")
        d = u.num2date(u.date2num(datetimex(-1, 1, 1)))
        assert (d.year == -1)
        assert (d.month == 1)
        assert (d.day == 1)
        assert (d.hour == 0)
        # test fix for issue #659 (proper treatment of negative time values).
        units = 'days since 1800-01-01 00:00:0.0'
        d = num2date(-657073, units, calendar='standard')
        assert (d.year == 1)
        assert (d.month == 1)
        assert (d.day == 1)
        assert (d.hour == 0)
        # issue 685: wrong time zone conversion
        # 'The following times all refer to the same moment: "18:30Z", "22:30+04", "1130-0700", and "15:00-03:30'
        # (https://en.wikipedia.org/w/index.php?title=ISO_8601&oldid=787811367#Time_offsets_from_UTC)
        # test num2date
        utc_date = datetime(2000, 1, 1, 18, 30)
        for units in ("hours since 2000-01-01 22:30+04:00",
                      "hours since 2000-01-01 11:30-07:00",
                      "hours since 2000-01-01 15:00-03:30"):
            d = num2date(0, units, calendar="standard")
            assert (numpy.abs((d - utc_date).total_seconds()) < 1.e-3)
            # also test with negative values to cover 2nd code path
            d = num2date(-1, units, calendar="standard")
            assert(numpy.abs((d - \
                (utc_date-timedelta(hours=1))).total_seconds()) < 1.e-3)

            n = date2num(utc_date, units, calendar="standard")
            # n should always be 0 as all units refer to the same point in time
            self.assertEqual(n, 0)
        # explicitly test 2nd code path for date2num
        units = "hours since 2000-01-01 22:30+04:00"
        n = date2num(utc_date, units, calendar="julian")
        # n should always be 0 as all units refer to the same point in time
        assert_almost_equal(n, 0)