dateutil · Sean-Kenneth-Doherty · May 17, 2026 · May 17, 2026 · May 17, 2026 · May 17, 2026
diff --git a/changelog.d/1492.bugfix.rst b/changelog.d/1492.bugfix.rst
@@ -0,0 +1 @@
+Fixed ``tzstr()`` raising ``TypeError`` when parsing bare ``GMT`` or ``UTC`` names without an explicit offset.
diff --git a/docs/conf.py b/docs/conf.py
@@ -286,6 +286,8 @@ def pointer_mock(*args, **kwargs):
     r'https://pgp.mit.edu',
     # MetaCPAN frequently returns 402 for automated link checkers
     r"https://metacpan.org/.*",
+    # Planetary Rings Node frequently times out for automated link checkers
+    r"https://pds-rings.seti.org(:443)?/.*",
 ]
 
 # Reduce problems with ephemeral failures

diff --git a/docs/exercises/index.rst b/docs/exercises/index.rst
@@ -125,7 +125,7 @@ To solve this exercise, copy-paste this script into a document, change anything
 Parsing a local tzname
 ----------------------
 
-    Three-character time zone abbreviations are *not* unique in that they do not explicitly map to a time zone. A list of time zone abbreviations in use can be found `here <https://www.timeanddate.com/time/zones/>`_. This means that parsing a datetime string such as ``'2018-01-01 12:30:30 CST'`` is ambiguous without context. Using :mod:`dateutil.parser` and :mod:`dateutil.tz`, it is possible to provide a context such that these local names are converted to proper time zones.
+    Three-character time zone abbreviations are *not* unique in that they do not explicitly map to a time zone. A list of time zone abbreviations in use can be found `here <https://en.wikipedia.org/wiki/List_of_time_zone_abbreviations>`_. This means that parsing a datetime string such as ``'2018-01-01 12:30:30 CST'`` is ambiguous without context. Using :mod:`dateutil.parser` and :mod:`dateutil.tz`, it is possible to provide a context such that these local names are converted to proper time zones.
 
 Problem 1
 *********
@@ -239,4 +239,3 @@ To solve this exercise, copy-paste this script into a document, change anything
 .. raw:: html
 
     </details>
-
diff --git a/src/dateutil/tz/tz.py b/src/dateutil/tz/tz.py
@@ -1074,7 +1074,7 @@ class tzstr(tzrange):
         support is removed in a future version.
 
     .. _`GNU C Library: TZ Variable`:
-        https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
+        https://sourceware.org/glibc/manual/latest/html_node/TZ-Variable.html
     """
     def __init__(self, s, posix_offset=False):
         global parser
@@ -1088,7 +1088,11 @@ def __init__(self, s, posix_offset=False):
 
         # Here we break the compatibility with the TZ variable handling.
         # GMT-3 actually *means* the timezone -3.
-        if res.stdabbr in ("GMT", "UTC") and not posix_offset:
+        if (
+            res.stdabbr in ("GMT", "UTC")
+            and res.stdoffset is not None
+            and not posix_offset
+        ):
             res.stdoffset *= -1
 
         # We must initialize it first, since _delta() needs
@@ -1537,7 +1541,7 @@ class GettzFunc(object):
 
 
         .. _`TZ variable`:
-            https://www.gnu.org/software/libc/manual/html_node/TZ-Variable.html
+            https://sourceware.org/glibc/manual/latest/html_node/TZ-Variable.html
 
         .. _`"same zone" semantics`:
             https://blog.ganssle.io/articles/2018/02/aware-datetime-arithmetic.html

diff --git a/tests/test_tz.py b/tests/test_tz.py
@@ -1471,6 +1471,14 @@ def testPosixOffset(self):
         self.assertEqual(datetime(2015, 1, 1, tzinfo=TZ2).utcoffset(),
                          timedelta(hours=+3))
 
+    def testBareUtcGmtOffset(self):
+        for tz_str in ("GMT", "UTC"):
+            TZ = tz.tzstr(tz_str)
+            dt = datetime(2015, 1, 1, tzinfo=TZ)
+
+            self.assertEqual(dt.tzname(), tz_str)
+            self.assertEqual(dt.utcoffset(), timedelta(0))
+
     def testStrInequalityUnsupported(self):
         TZS = tz.tzstr('EST5EDT')
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fixed ``tzstr()`` raising ``TypeError`` when parsing bare ``GMT`` or ``UTC`` names without an explicit offset.