Backport of fix for bug of year/<week of year>/<day of week> calculation that

didn't handle %U for years starting on Monday.

2 files changed, 30 insertions, 14 deletions

diff --git a/Lib/_strptime.py b/Lib/_strptime.py
index d3959ae754..41162bb0fc 100644
--- a/Lib/_strptime.py
+++ b/Lib/_strptime.py
@@ -518,25 +518,27 @@ def strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
     # If we know the week of the year and what day of that week, we can figure
     # out the Julian day of the year
     # Calculations below assume 0 is a Monday
-    if julian == -1 and week_of_year != -1 and weekday != -1 and year != -1:
-        # Adjust for U directive so that calculations are not dependent on
-        # directive used to figure out week of year
-        if weekday == 6 and week_of_year_start == 6:
-            week_of_year -= 1
-        # For some reason when Dec 31 falls on a Monday the week of the year is
-        # off by a week; verified on both OS X and Solaris.
-        elif weekday == 0 and week_of_year_start == 6 and week_of_year >= 52:
-            week_of_year += 1
+    if julian == -1 and week_of_year != -1 and weekday != -1:
         # Calculate how many days in week 0
         first_weekday = datetime_date(year, 1, 1).weekday()
         preceeding_days = 7 - first_weekday
         if preceeding_days == 7:
             preceeding_days = 0
+        # Adjust for U directive so that calculations are not dependent on
+        # directive used to figure out week of year
+        if weekday == 6 and week_of_year_start == 6:
+            week_of_year -= 1
+        # If a year starts and ends on a Monday but a week is specified to
+        # start on a Sunday we need to up the week to counter-balance the fact
+        # that with %W that first Monday starts week 1 while with %U that is
+        # week 0 and thus shifts everything by a week
+        if weekday == 0 and first_weekday == 0 and week_of_year_start == 6:
+            week_of_year += 1
         # If in week 0, then just figure out how many days from Jan 1 to day of
         # week specified, else calculate by multiplying week of year by 7,
         # adding in days in week 0, and the number of days from Monday to the
         # day of the week
-        if not week_of_year:
+        if week_of_year == 0:
             julian = 1 + weekday - first_weekday
         else:
             days_to_week = preceeding_days + (7 * (week_of_year - 1))
diff --git a/Lib/test/test_strptime.py b/Lib/test/test_strptime.py
index 09b59212d6..23466a4a59 100644
--- a/Lib/test/test_strptime.py
+++ b/Lib/test/test_strptime.py
@@ -457,21 +457,35 @@ class CalculationTests(unittest.TestCase):
         def test_helper(ymd_tuple, test_reason):
             for directive in ('W', 'U'):
                 format_string = "%%Y %%%s %%w" % directive
-                strp_input = datetime_date(*ymd_tuple).strftime(format_string)
+                dt_date = datetime_date(*ymd_tuple)
+                strp_input = dt_date.strftime(format_string)
                 strp_output = _strptime.strptime(strp_input, format_string)
                 self.failUnless(strp_output[:3] == ymd_tuple,
-                        "%s(%s) test failed w/ '%s': %s != %s" %
+                        "%s(%s) test failed w/ '%s': %s != %s (%s != %s)" %
                             (test_reason, directive, strp_input,
-                                strp_output[:3], ymd_tuple[:3]))
+                                strp_output[:3], ymd_tuple,
+                                strp_output[7], dt_date.timetuple()[7]))
         test_helper((1901, 1, 3), "week 0")
         test_helper((1901, 1, 8), "common case")
         test_helper((1901, 1, 13), "day on Sunday")
         test_helper((1901, 1, 14), "day on Monday")
         test_helper((1905, 1, 1), "Jan 1 on Sunday")
         test_helper((1906, 1, 1), "Jan 1 on Monday")
+        test_helper((1906, 1, 7), "first Sunday in a year starting on Monday")
         test_helper((1905, 12, 31), "Dec 31 on Sunday")
         test_helper((1906, 12, 31), "Dec 31 on Monday")
-
+        test_helper((2008, 12, 29), "Monday in the last week of the year")
+        test_helper((2008, 12, 22), "Monday in the second-to-last week of the "
+                                    "year")
+        test_helper((1978, 10, 23), "randomly chosen date")
+        test_helper((2004, 12, 18), "randomly chosen date")
+        test_helper((1978, 10, 23), "year starting and ending on Monday while "
+                                        "date not on Sunday or Monday")
+        test_helper((1917, 12, 17), "year starting and ending on Monday with "
+                                        "a Monday not at the beginning or end "
+                                        "of the year")
+        test_helper((1917, 12, 31), "Dec 31 on Monday with year starting and "
+                                        "ending on Monday")
 
 
 class CacheTests(unittest.TestCase):