R. David Murray added the comment:
from the man page for strptime:
%w The weekday number (0-6) with Sunday = 0.
%W The week number with Monday the first day of the week (0-53).
The first Monday of January is the first day of week 1.
Python's documentation
New submission from Steve J Borba:
OS: Windows 7 Professional (64-bit)
Hardware: Intel
datetime.strptime returns an incorrect value when calculating a date using a
week number format, such as "%Y-%W-%w" (Year-Week-Weekday). The value returned
for weekday '0' of a given week is consistently 7 d
