Issue #9764 has been updated by tadayoshi funaba.

Status changed from Assigned to Rejected

----------------------------------------
Bug #9764: Date and DateTime strptime and strftime not supporting proper Week Numbering for Monday vs Sunday as start day and %G causes ignore of all other format arguments
https://bugs.ruby-lang.org/issues/9764#change-46276

* Author: Steve R
* Status: Rejected
* Priority: Low
* Assignee: tadayoshi funaba
* Category: 
* Target version: 
* ruby -v: ruby 2.0.0p247 (2013-06-27 revision 41674) [x86_64-darwin12.4.0]
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN
----------------------------------------
Date and DateTime strftime and strptime are not supporting %U (0-53 Week Numbers as defined in strptime): 
http://www.ruby-doc.org/stdlib-2.1.1/libdoc/date/rdoc/Date.html#method-i-strftime

Some examples that are not producing expected results/output:

1. require 'date'; puts Date.new(2013,12,30).strftime("%G %U")  # 2014 52  -- How is this Week 52 of 2013??

2. require 'date'; puts Date.strptime("2014 01","%G %U")  # 2013-12-30 -- This should really be 2013-12-29 as the 29th is the sunday and the 30th is the Monday, and %U should be using Sunday as the first day of week.

3. The following three examples all produce the same result but really should not.  Even if you change the week number to any number it still stays at the same output/result.  It seems like there is a bug related to %G that ignores all other commands:

puts Date.strptime('00 2014', '%U %G')  # 2013-12-30
puts Date.strptime('00 2014', '%W %G')  # 2013-12-30
puts Date.strptime('2014W011', '%GW%V%u')  # 2013-12-30


Additionally one would expect the following two lines to produce the same results:
puts Date.strptime('00 2014', '%W %G')  # 2013-12-30
puts Date.strptime('00 2014', '%W %Y')  # Invalid Date Argument





-- 
https://bugs.ruby-lang.org/