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[Datepicker] First or last week of the year is wrong

in Using jQuery UI • 6 years ago

Hi,
I have the following problem:
I have 'showWeek ' option set to 'true '. The first week of the year is shown as '52' (the last week of the previous year). You can observe this behaviour in this sample (https://jqueryui.com/resources/demos/datepicker/show-week.html).

Steps to reproduce:
1. Open the sample
2. Navigate to January 2012
3. Take a look at the first week

Actual result:
The week number is '52'
Screenshot attached

Expected result:
The week number should be '1'

Note:
The same issue can be reproduced if you navigate to December 2014 and have a look at the last week. Its number is '1'

Attachments

screenshot.png
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Replies(3)

Sµßhrånil∂

Re: [Datepicker] First or last week of the year is wrong

6 years ago

There is nothing wrong with that, its the way how week calculated following ISO 8601 serenaded.

This is ISO stranded for week calculation

Week dates

Main article: ISO week date

YYYY-Www or YYYYWww

YYYY-Www-D or YYYYWwwD

Week date representations are in the format as shown in the box to the right. [YYYY] indicates the ISO week-numbering year which is slightly different from the traditional Gregorian calendar year (see below). [Www] is the week number prefixed by the letter W, from W01 through W53. [D] is the weekday number, from 1 through 7, beginning with Monday and ending with Sunday. This form is popular in the manufacturing industries.

There are mutually equivalent descriptions of week 01:

the week with the year's first Thursday in it (the formal ISO definition),

the week with 4 January in it,

the first week with the majority (four or more) of its days in the starting year, and

the week starting with the Monday in the period 29 December – 4 January.

If 1 January is on a Monday, Tuesday, Wednesday or Thursday, it is in week 01. If 1 January is on a Friday, Saturday or Sunday, it is in week 52 or 53 of the previous year (there is no week 00). 28 December is always in the last week of its year.

The week number can be described by counting the Thursdays: week 12 contains the 12th Thursday of the year.

The ISO week-numbering year starts at the first day (Monday) of week 01 and ends at the Sunday before the new ISO year (hence without overlap or gap). It consists of 52 or 53 full weeks. The ISO week-numbering year number deviates from the number of the traditional Gregorian calendar year on a Friday, Saturday, and Sunday, or a Saturday and Sunday, or just a Sunday, at the start of the traditional Gregorian calendar year (which are at the end of the previous ISO week-numbering year) and a Monday, Tuesday and Wednesday, or a Monday and Tuesday, or just a Monday, at the end of the traditional Gregorian calendar year (which are in week 01 of the next ISO week-numbering year). For Thursdays, the ISO week-numbering year number is always equal to the traditional Gregorian calendar year number.

Examples:

Monday 29 December 2008 is written "2009-W01-1"

Sunday 3 January 2010 is written "2009-W53-7"

For an overview of week numbering systems see week number. The US system has weeks from Sunday through Saturday, and partial weeks at the beginning and the end of the year. An advantage is that no separate year numbering like the ISO week-numbering year is needed, while correspondence of lexicographical order and chronological order is preserved.