diff --git a/Lib/http/cookies.py b/Lib/http/cookies.py
index 35ac2dc6ae2..57791c6ab08 100644
--- a/Lib/http/cookies.py
+++ b/Lib/http/cookies.py
@@ -184,8 +184,13 @@ def _quote(str):
         return '"' + str.translate(_Translator) + '"'
 
 
-_OctalPatt = re.compile(r"\\[0-3][0-7][0-7]")
-_QuotePatt = re.compile(r"[\\].")
+_unquote_sub = re.compile(r'\\(?:([0-3][0-7][0-7])|(.))').sub
+
+def _unquote_replace(m):
+    if m[1]:
+        return chr(int(m[1], 8))
+    else:
+        return m[2]
 
 def _unquote(str):
     # If there aren't any doublequotes,
@@ -205,36 +210,13 @@ def _unquote(str):
     #    \012 --> \n
     #    \"   --> "
     #
-    i = 0
-    n = len(str)
-    res = []
-    while 0 <= i < n:
-        o_match = _OctalPatt.search(str, i)
-        q_match = _QuotePatt.search(str, i)
-        if not o_match and not q_match:              # Neither matched
-            res.append(str[i:])
-            break
-        # else:
-        j = k = -1
-        if o_match:
-            j = o_match.start(0)
-        if q_match:
-            k = q_match.start(0)
-        if q_match and (not o_match or k < j):     # QuotePatt matched
-            res.append(str[i:k])
-            res.append(str[k+1])
-            i = k + 2
-        else:                                      # OctalPatt matched
-            res.append(str[i:j])
-            res.append(chr(int(str[j+1:j+4], 8)))
-            i = j + 4
-    return _nulljoin(res)
+    return _unquote_sub(_unquote_replace, str)
 
 # The _getdate() routine is used to set the expiration time in the cookie's HTTP
 # header.  By default, _getdate() returns the current time in the appropriate
 # "expires" format for a Set-Cookie header.  The one optional argument is an
 # offset from now, in seconds.  For example, an offset of -3600 means "one hour
-# ago".  The offset may be a floating point number.
+# ago".  The offset may be a floating-point number.
 #
 
 _weekdayname = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
@@ -442,9 +424,11 @@ def OutputString(self, attrs=None):
     (                              # Optional group: there may not be a value.
     \s*=\s*                          # Equal Sign
     (?P<val>                         # Start of group 'val'
-    "(?:[^\\"]|\\.)*"                  # Any doublequoted string
+    "(?:[^\\"]|\\.)*"                  # Any double-quoted string
     |                                  # or
-    \w{3},\s[\w\d\s-]{9,11}\s[\d:]{8}\sGMT  # Special case for "expires" attr
+    # Special case for "expires" attr
+    (\w{3,6}day|\w{3}),\s              # Day of the week or abbreviated day
+    [\w\d\s-]{9,11}\s[\d:]{8}\sGMT     # Date and time in specific format
     |                                  # or
     [""" + _LegalValueChars + r"""]*      # Any word or empty string
     )                                # End of group 'val'
diff --git a/Lib/test/test_http_cookies.py b/Lib/test/test_http_cookies.py
index 6072c7e15e9..3e0b4d1d5ca 100644
--- a/Lib/test/test_http_cookies.py
+++ b/Lib/test/test_http_cookies.py
@@ -1,13 +1,15 @@
 # Simple test suite for http/cookies.py
 
 import copy
-from test.support import run_unittest, run_doctest
 import unittest
+import doctest
 from http import cookies
 import pickle
+from test import support
+from test.support.testcase import ExtraAssertions
 
 
-class CookieTests(unittest.TestCase):
+class CookieTests(unittest.TestCase, ExtraAssertions):
 
     def test_basic(self):
         cases = [
@@ -58,6 +60,90 @@ def test_basic(self):
             for k, v in sorted(case['dict'].items()):
                 self.assertEqual(C[k].value, v)
 
+    def test_obsolete_rfc850_date_format(self):
+        # Test cases with different days and dates in obsolete RFC 850 format
+        test_cases = [
+            # from RFC 850, change EST to GMT
+            # https://datatracker.ietf.org/doc/html/rfc850#section-2
+            {
+                'data': 'key=value; expires=Saturday, 01-Jan-83 00:00:00 GMT',
+                'output': 'Saturday, 01-Jan-83 00:00:00 GMT'
+            },
+            {
+                'data': 'key=value; expires=Friday, 19-Nov-82 16:59:30 GMT',
+                'output': 'Friday, 19-Nov-82 16:59:30 GMT'
+            },
+            # from RFC 9110
+            # https://www.rfc-editor.org/rfc/rfc9110.html#section-5.6.7-6
+            {
+                'data': 'key=value; expires=Sunday, 06-Nov-94 08:49:37 GMT',
+                'output': 'Sunday, 06-Nov-94 08:49:37 GMT'
+            },
+            # other test cases
+            {
+                'data': 'key=value; expires=Wednesday, 09-Nov-94 08:49:37 GMT',
+                'output': 'Wednesday, 09-Nov-94 08:49:37 GMT'
+            },
+            {
+                'data': 'key=value; expires=Friday, 11-Nov-94 08:49:37 GMT',
+                'output': 'Friday, 11-Nov-94 08:49:37 GMT'
+            },
+            {
+                'data': 'key=value; expires=Monday, 14-Nov-94 08:49:37 GMT',
+                'output': 'Monday, 14-Nov-94 08:49:37 GMT'
+            },
+        ]
+
+        for case in test_cases:
+            with self.subTest(data=case['data']):
+                C = cookies.SimpleCookie()
+                C.load(case['data'])
+
+                # Extract the cookie name from the data string
+                cookie_name = case['data'].split('=')[0]
+
+                # Check if the cookie is loaded correctly
+                self.assertIn(cookie_name, C)
+                self.assertEqual(C[cookie_name].get('expires'), case['output'])
+
+    def test_unquote(self):
+        cases = [
+            (r'a="b=\""', 'b="'),
+            (r'a="b=\\"', 'b=\\'),
+            (r'a="b=\="', 'b=='),
+            (r'a="b=\n"', 'b=n'),
+            (r'a="b=\042"', 'b="'),
+            (r'a="b=\134"', 'b=\\'),
+            (r'a="b=\377"', 'b=\xff'),
+            (r'a="b=\400"', 'b=400'),
+            (r'a="b=\42"', 'b=42'),
+            (r'a="b=\\042"', 'b=\\042'),
+            (r'a="b=\\134"', 'b=\\134'),
+            (r'a="b=\\\""', 'b=\\"'),
+            (r'a="b=\\\042"', 'b=\\"'),
+            (r'a="b=\134\""', 'b=\\"'),
+            (r'a="b=\134\042"', 'b=\\"'),
+        ]
+        for encoded, decoded in cases:
+            with self.subTest(encoded):
+                C = cookies.SimpleCookie()
+                C.load(encoded)
+                self.assertEqual(C['a'].value, decoded)
+
+    @support.requires_resource('cpu')
+    def test_unquote_large(self):
+        #n = 10**6
+        n = 10**4 # XXX: RUSTPYTHON; This takes more than 10 minutes to run. lower to 4
+        for encoded in r'\\', r'\134':
+            with self.subTest(encoded):
+                data = 'a="b=' + encoded*n + ';"'
+                C = cookies.SimpleCookie()
+                C.load(data)
+                value = C['a'].value
+                self.assertEqual(value[:3], 'b=\\')
+                self.assertEqual(value[-2:], '\\;')
+                self.assertEqual(len(value), n + 3)
+
     def test_load(self):
         C = cookies.SimpleCookie()
         C.load('Customer="WILE_E_COYOTE"; Version=1; Path=/acme')
@@ -96,7 +182,7 @@ def test_special_attrs(self):
         C = cookies.SimpleCookie('Customer="WILE_E_COYOTE"')
         C['Customer']['expires'] = 0
         # can't test exact output, it always depends on current date/time
-        self.assertTrue(C.output().endswith('GMT'))
+        self.assertEndsWith(C.output(), 'GMT')
 
         # loading 'expires'
         C = cookies.SimpleCookie()
@@ -479,9 +565,11 @@ def test_repr(self):
                 r'Set-Cookie: key=coded_val; '
                 r'expires=\w+, \d+ \w+ \d+ \d+:\d+:\d+ \w+')
 
-def test_main():
-    run_unittest(CookieTests, MorselTests)
-    run_doctest(cookies)
+
+def load_tests(loader, tests, pattern):
+    tests.addTest(doctest.DocTestSuite(cookies))
+    return tests
+
 
 if __name__ == '__main__':
-    test_main()
+    unittest.main()