From 4d94743c28af939864e870f556f8b656fbd3b774 Mon Sep 17 00:00:00 2001
From: Brett Cannon <bcannon@gmail.com>
Date: Tue, 22 Sep 2009 00:29:48 +0000
Subject: [PATCH] When range checking was added to time.strftime() a check was
 placed on tm_isdst to make sure it fell within [-1, 1] just in case someone
 implementing strftime() in libc was stupid enough to assume this. Turns out,
 though, some OSs (e.g. zOS) are stupid enough to use values outside of this
 range for time structs created by the system itself. So instead of throwing a
 ValueError, tm_isdst is now normalized before being passed to strftime().

Fixes issue #6823. Thanks Robert Shapiro for diagnosing the problem and
contributing an initial patch.
---
 Lib/test/test_time.py |  5 -----
 Misc/ACKS             |  1 +
 Misc/NEWS             |  4 ++++
 Modules/timemodule.c  | 12 +++++++-----
 4 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index 965f7e2fef3..6683de6ea20 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -87,11 +87,6 @@ class TimeTestCase(unittest.TestCase):
                             (1900, 1, 1, 0, 0, 0, 0, -1, -1))
         self.assertRaises(ValueError, time.strftime, '',
                             (1900, 1, 1, 0, 0, 0, 0, 367, -1))
-        # Check daylight savings flag [-1, 1]
-        self.assertRaises(ValueError, time.strftime, '',
-                            (1900, 1, 1, 0, 0, 0, 0, 1, -2))
-        self.assertRaises(ValueError, time.strftime, '',
-                            (1900, 1, 1, 0, 0, 0, 0, 1, 2))
 
     def test_default_values_for_zero(self):
         # Make sure that using all zeros uses the proper default values.
diff --git a/Misc/ACKS b/Misc/ACKS
index e0bd435005a..4889be8aeec 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -669,6 +669,7 @@ Jerry Seutter
 Denis Severson
 Ian Seyer
 Ha Shao
+Richard Shapiro
 Bruce Sherwood
 Pete Shinners
 Michael Shiplett
diff --git a/Misc/NEWS b/Misc/NEWS
index 89cbf3ca460..15db19963ec 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -1340,6 +1340,10 @@ C-API
 Extension Modules
 -----------------
 
+- Issue #6823: Allow time.strftime() to accept a tuple with a isdst field
+  outside of the range of [-1, 1] by normalizing the value to within that
+  range.
+
 - Issue #6877: Make it possible to link the readline extension to libedit
   on OSX.
 
diff --git a/Modules/timemodule.c b/Modules/timemodule.c
index 2f4092d64e1..624405eb378 100644
--- a/Modules/timemodule.c
+++ b/Modules/timemodule.c
@@ -464,11 +464,13 @@ time_strftime(PyObject *self, PyObject *args)
             PyErr_SetString(PyExc_ValueError, "day of year out of range");
             return NULL;
         }
-        if (buf.tm_isdst < -1 || buf.tm_isdst > 1) {
-            PyErr_SetString(PyExc_ValueError,
-                            "daylight savings flag out of range");
-            return NULL;
-        }
+	/* Normalize tm_isdst just in case someone foolishly implements %Z
+	   based on the assumption that tm_isdst falls within the range of
+	   [-1, 1] */
+        if (buf.tm_isdst < -1)
+	    buf.tm_isdst = -1;
+	else if (buf.tm_isdst > 1)
+	    buf.tm_isdst = 1;
 
 #ifdef MS_WINDOWS
 	/* check that the format string contains only valid directives */