Bug #9372: Date function cweek reports innaccurately for the date December 30, 2013

• Status: Rejected
• Assignee: tadf (tadayoshi funaba)
• Target version: -
• ruby -v: 2.0.0p247
• Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN

[pblesi (Patrick Blesi)]

Date function cweek reports innaccurately for the date December 30, 2013. The current week is reported as 1 instead of 53.

[pblesi (Patrick Blesi)]

I've added some code for extra clarity.

2.0.0p247 :017 > require 'date'
 => true 
2.0.0p247 :018 > d = Date.new(2013,12,30)
 => #<Date: 2013-12-30 ((2456657j,0s,0n),+0s,2299161j)> 
2.0.0p247 :019 > d.cweek
 => 1 

2.0.0p247 :005 > d = Date.new(2013, 12, 29)
 => #<Date: 2013-12-29 ((2456656j,0s,0n),+0s,2299161j)> 
2.0.0p247 :006 > d.cweek
 => 52 

[tadf (tadayoshi funaba)]

• Status changed from Open to Assigned
• Assignee set to tadf (tadayoshi funaba)

[tadf (tadayoshi funaba)]

• Status changed from Assigned to Rejected

A period of time of seven days within a calendar year, starting on a
Monday and identified by its ordinal number within the year; the first
calendar week of the year is the one that includes the first Thursday
of that year. In the Gregorian calendar, this is equivalent to the
week which includes 4 January.

[duerst (Martin Dürst)]

tadf (tadayoshi funaba) wrote:

A period of time of seven days within a calendar year, starting on a
Monday and identified by its ordinal number within the year; the first
calendar week of the year is the one that includes the first Thursday
of that year. In the Gregorian calendar, this is equivalent to the
week which includes 4 January.

This may not yet be completely clear, because it says "within a [calendar] year" twice. The following quote, from http://en.wikipedia.org/wiki/ISO_week_date, is even clearer:

"ISO week-numbering years have a year numbering which is approximately the same as the Gregorian years, but not exactly since an ISO week-numbering year (also called ISO year or week year informally) has 52 or 53 full weeks. That is 364 or 371 days instead of the usual 365 or 366 days."

It may be a good idea to add the following example (borrowed from cwyear)

Date.new(2000,1,1).cweek         #=> 53, see Date#cwyear

Tadayoshi, I can do that if you are okay.

[nobu (Nobuyoshi Nakada)]

• Has duplicate Bug #9809: Date.new(2000,1,1).cweek should == 1 added

[nobu (Nobuyoshi Nakada)]

This is a repeated question, so it feels nice to add examples.

[esaari (Eric Saari)]

Nobuyoshi Nakada wrote:

This is a repeated question, so it feels nice to add examples.

Even though this is a closed issue, I am seeing the same issue for the years 2018 and 2019:

$> date = Date.new(2018,12,31)
=> #<Date: 2018-12-31 ((2458484j,0s,0n),+0s,2299161j)>
$> date.cweek
=> 1
$> date = Date.new(2019,12,31)
=> #<Date: 2019-12-31 ((2458849j,0s,0n),+0s,2299161j)>
$> date.cweek
=> 1

Can this same issue apply for two calendar years in a row?