Mar 2, 2025 · Mar 2, 2025 · Mar 2, 2025 · Mar 3, 2025 · Mar 16, 2025 · May 19, 2025
diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
        t = (self - epoch) // timedelta(0, 1)
        def local(u):
            y, m, d, hh, mm, ss = _time.localtime(u)[:6]
            return (datetime(y, m, d, hh, mm, ss) - epoch) // timedelta(0, 1)
            try:
                return ((datetime(y, m, d, hh, mm, ss) - epoch) //
                        timedelta(0, 1))
            except (ValueError, OverflowError):
                return u

        # Our goal is to solve t = local(u) for u.
        a = local(t) - t
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
        with self.assertRaises(TypeError):
            dt_broken.astimezone()

        dt_big = self.theclass(9999, 12, 31, 23, 59, 59)
        dt_big_utc = dt_big.replace(hour=19,
                                    tzinfo=timezone(timedelta(hours=-4), 'EDT'))
        self.assertEqual(dt_big_utc,
                         dt_big.replace(tzinfo=timezone.utc).astimezone())

        other_tz = timezone(timedelta(hours=+4), '+04')
        dt_other_tz = dt_big.replace(tzinfo=other_tz)
        dt_utc_tz = dt_big.replace(tzinfo=timezone.utc)
        self.assertEqual(dt_other_tz, dt_other_tz.astimezone(tz=other_tz))
        self.assertEqual(dt_utc_tz, dt_utc_tz.astimezone(tz=timezone.utc))

    def test_subclass_datetime(self):

        class C(self.theclass):
diff --git a/Modules/_datetimemodule.c b/Modules/_datetimemodule.c
 {
    struct tm local_time;
    time_t t;
    long long old_u = u;
    u -= epoch;
    t = u;
    if (t != u) {
    }
    if (_PyTime_localtime(t, &local_time) != 0)
        return -1;
    return utc_to_seconds(local_time.tm_year + 1900,

    // Check edge cases
    int year = local_time.tm_year + 1900;
    if (year < MINYEAR || year > MAXYEAR) {
        Py_DECREF(year);
        return old_u;
    }
    return utc_to_seconds(year,
                          local_time.tm_mon + 1,
                          local_time.tm_mday,
                          local_time.tm_hour,
Original file line number	Diff line number	Diff line change
Expand Up		@@ -1989,7 +1989,11 @@ def _mktime(self):
		t = (self - epoch) // timedelta(0, 1)
		def local(u):
		y, m, d, hh, mm, ss = _time.localtime(u)[:6]
		return (datetime(y, m, d, hh, mm, ss) - epoch) // timedelta(0, 1)
		try:
		return ((datetime(y, m, d, hh, mm, ss) - epoch) //
		timedelta(0, 1))
		except (ValueError, OverflowError):
		return u

		# Our goal is to solve t = local(u) for u.
		a = local(t) - t
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -3122,6 +3122,18 @@ def dst(self, dt): return 1
		with self.assertRaises(TypeError):
		dt_broken.astimezone()

		dt_big = self.theclass(9999, 12, 31, 23, 59, 59)
Copy link Member pganssleMay 19, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. I don't love that the original style violates the one-assert-per-test style, and we should probably not continue that. Let's move this into its own method, like`test_astimezone_max` and`test_astimezone_min`. We can test the values near`datetime.min` and`datetime.max` separately, and use`self.subTest` to try a few different values for time zone. I'm not sure if`@support.run_with_tz` can be parameterized, but if it can we should try it on a few different time zones.
		dt_big_utc = dt_big.replace(hour=19,
		tzinfo=timezone(timedelta(hours=-4), 'EDT'))
		self.assertEqual(dt_big_utc,
		dt_big.replace(tzinfo=timezone.utc).astimezone())

		other_tz = timezone(timedelta(hours=+4), '+04')
		dt_other_tz = dt_big.replace(tzinfo=other_tz)
		dt_utc_tz = dt_big.replace(tzinfo=timezone.utc)
		self.assertEqual(dt_other_tz, dt_other_tz.astimezone(tz=other_tz))
		self.assertEqual(dt_utc_tz, dt_utc_tz.astimezone(tz=timezone.utc))

		def test_subclass_datetime(self):

		class C(self.theclass):
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -5415,6 +5415,7 @@
		{
		struct tm local_time;
		time_t t;
		long long old_u = u;
		u -= epoch;
		t = u;
		if (t != u) {
Expand All		@@ -5424,7 +5425,14 @@
		}
		if (_PyTime_localtime(t, &local_time) != 0)
		return -1;
		return utc_to_seconds(local_time.tm_year + 1900,

		// Check edge cases
Copy link Member pganssleMay 19, 2025 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others.Learn more. This should be more specific — what this code does is very opaque, so we should have a "why" comment here. Something like "When the year is outside the allowed year boundaries, return the original utc timestamp because ".
		int year = local_time.tm_year + 1900;
		if (year < MINYEAR \|\| year > MAXYEAR) {
		Py_DECREF(year);
Check warning on line 5432 in Modules/_datetimemodule.c View workflow job for this annotation GitHub Actions/ Windows / build (arm64) `'type cast': conversion from 'int' to 'PyObject ' of greater size [D:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]` Check warning on line 5432 in Modules/_datetimemodule.c View workflow job for this annotation GitHub Actions/ Windows (free-threading) / build (arm64) `'type cast': conversion from 'int' to 'PyObject ' of greater size [D:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]` Check warning on line 5432 in Modules/_datetimemodule.c View workflow job for this annotation GitHub Actions/ Windows / build and test (x64) `'type cast': conversion from 'int' to 'PyObject ' of greater size [D:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]` Check warning on line 5432 in Modules/_datetimemodule.c View workflow job for this annotation GitHub Actions/ Windows (free-threading) / build and test (x64) `'type cast': conversion from 'int' to 'PyObject ' of greater size [D:\a\cpython\cpython\PCbuild\pythoncore.vcxproj]`
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		return old_u;
		}
		return utc_to_seconds(year,
		local_time.tm_mon + 1,
		local_time.tm_mday,
		local_time.tm_hour,
Expand Down