diff -r 1383a260b66d Lib/_strptime.py
--- a/Lib/_strptime.py	Wed Feb 10 01:17:51 2016 +0000
+++ b/Lib/_strptime.py	Tue Feb 09 23:13:28 2016 +0100
@@ -462,6 +462,9 @@
         week_starts_Mon = True if week_of_year_start == 0 else False
         julian = _calc_julian_from_U_or_W(year, week_of_year, weekday,
                                             week_starts_Mon)
+        if julian < 0:
+            year -= 1
+            julian = datetime_date(year, 12, 31).timetuple().tm_yday + julian
     # Cannot pre-calculate datetime_date() since can change in Julian
     # calculation and thus could have different value for the day of the week
     # calculation.