BUG: is_utc(dateutil_utc) (#39276)

Author: jbrockmendel

doc/source/whatsnew/v1.3.0.rst

@@ -247,7 +247,7 @@ Timedelta
 Timezones
 ^^^^^^^^^
 - Bug in different ``tzinfo`` objects representing UTC not being treated as equivalent (:issue:`39216`)
--
+- Bug in ``dateutil.tz.gettz("UTC")`` not being recognized as equivalent to other UTC-representing tzinfos (:issue:`39276`)
 -
 
 Numeric

pandas/_libs/tslibs/timezones.pyx

@@ -30,11 +30,18 @@ from pandas._libs.tslibs.util cimport get_nat, is_integer_object
 cdef int64_t NPY_NAT = get_nat()
 cdef tzinfo utc_stdlib = timezone.utc
 cdef tzinfo utc_pytz = UTC
+cdef tzinfo utc_dateutil_str = dateutil_gettz("UTC")  # NB: *not* the same as tzutc()
+
 
 # ----------------------------------------------------------------------
 
 cpdef inline bint is_utc(tzinfo tz):
-    return tz is utc_pytz or tz is utc_stdlib or isinstance(tz, _dateutil_tzutc)
+    return (
+        tz is utc_pytz
+        or tz is utc_stdlib
+        or isinstance(tz, _dateutil_tzutc)
+        or tz is utc_dateutil_str
+    )
 
 
 cdef inline bint is_tzlocal(tzinfo tz):

pandas/conftest.py

@@ -1041,6 +1041,9 @@ def utc_fixture(request):
     return request.param
 
 
+utc_fixture2 = utc_fixture
+
+
 # ----------------------------------------------------------------
 # Dtypes
 # ----------------------------------------------------------------

pandas/tests/tslibs/test_timezones.py

@@ -9,6 +9,11 @@
 from pandas import Timestamp
 
 
+def test_is_utc(utc_fixture):
+    tz = timezones.maybe_get_tz(utc_fixture)
+    assert timezones.is_utc(tz)
+
+
 @pytest.mark.parametrize("tz_name", list(pytz.common_timezones))
 def test_cache_keys_are_distinct_for_pytz_vs_dateutil(tz_name):
     if tz_name == "UTC":
@@ -56,6 +61,12 @@ def test_tzlocal_is_not_utc():
     assert not timezones.tz_compare(tz, dateutil.tz.tzutc())
 
 
+def test_tz_compare_utc(utc_fixture, utc_fixture2):
+    tz = timezones.maybe_get_tz(utc_fixture)
+    tz2 = timezones.maybe_get_tz(utc_fixture2)
+    assert timezones.tz_compare(tz, tz2)
+
+
 @pytest.fixture(
     params=[
         (pytz.timezone("US/Eastern"), lambda tz, x: tz.localize(x)),