gh-137976: fix available_timezones to prevent reporting an invalid IANA zone name: localtime

Doc/library/zoneinfo.rst

@@ -349,7 +349,7 @@ Functions
 
     This function only includes canonical zone names and does not include
     "special" zones such as those under the ``posix/`` and ``right/``
-    directories, or the ``posixrules`` zone.
+    directories, the ``posixrules``  or the ``localtime`` zone.
 
     .. caution::
 

Lib/test/test_zoneinfo/test_zoneinfo.py

@@ -1941,6 +1941,21 @@ def test_exclude_posixrules(self):
                 actual = self.module.available_timezones()
                 self.assertEqual(actual, expected)
 
+    def test_exclude_localtime(self):
+        expected = {
+            "America/New_York",
+            "Europe/London",
+        }
+
+        tree = list(expected) + ["localtime"]
+
+        with tempfile.TemporaryDirectory() as td:
+            for key in tree:
+                self.touch_zone(key, td)
+
+            with self.tzpath_context([td]):
+                actual = self.module.available_timezones()
+                self.assertEqual(actual, expected)
 
 class CTestModule(TestModule):
     module = c_zoneinfo

Lib/zoneinfo/_tzpath.py

@@ -170,6 +170,10 @@ def valid_key(fpath):
         # posixrules is a special symlink-only time zone where it exists, it
         # should not be included in the output
         valid_zones.remove("posixrules")
+    if "localtime" in valid_zones:
+        # localtime is a special symlink-only time zone where it exists, it
+        # should not be included in the output
+        valid_zones.remove("localtime")
 
     return valid_zones
 

Misc/NEWS.d/next/Core_and_Builtins/2025-08-21-01-46-39.gh-issue-137976.p4sb4x.rst

@@ -0,0 +1 @@
+Removed ``localtime`` from the list of reported system timezones.