Date filter returns wrong week number

[Kamilius]

I've just met a case, when date filter returns next week number instead of this week's number for given date.
Today is Sunday, 14 December 2014, week 50.

var weekNum = $filter('date')(new Date(2014, 11, 14), 'ww'); //returns 51 instead of 50

I suppose that the reason for this is that in North American countries a start of the week is Sunday. If it's so, how to correct this kind of behaviour? Because I'm living in Europe and need Monday-Sunday week instead of Sunday - Saturday.

Edit:
In AngularJS documentation - 'ww' returns ISO-8601 week, but considering my issue, it's not ISO-8601 as this standard has Monday as a start of the week.
https://docs.angularjs.org/api/ng/filter/date
http://en.wikipedia.org/wiki/Seven-day_week#Week_numbering

Edit2:
AngularJS v1.3.0
Added locale 'uk-ua'

[pkozlowski-opensource]

@Kamilius you are right on both fronts:

• currently the data filter is not really ISO-8601 compliant, we are going to correct the docs in docs(dateFilter): fix docs to match implementation for week no formatting #10445 as we don't want to have full ISO-8601 compatibility
• yes, the current implementation assumes Sun to be the first day of the week - unfortunately as of today we don't have any means of configuring this / pulling this info from the locale.

I'm going to mark it as a feature request to have the first day of a week being taken from a locale instead of being fixed for Sun

//cc: @yannickadam

[Kamilius]

@pkozlowski-opensource That's a bit not good, so I suppose you should correct this in documentation than.
Still managed to fix it in following manner:

var todayDate = new Date(), 
    currentWeek = +$filter('date')(new Date(todayDate.getFullYear(), todayDate.getMonth(), todayDate.getDate()), 'ww', 'UTC')

todayDate is created to set a new date with hours/minutes/seconds equal to 0.
I suppose it's just substracting "2"(as my timezone is UTC+2) and in case with blank hours - gives me previous week instead of a "next".
It solves my problems for now, but don't know how it will work in different timzeones.

Still thanks for an answer. Looking forward for more flexibility in this case.

[pkozlowski-opensource]

That's a bit not good, so I suppose you should correct this in documentation than.

@Kamilius could you elaborate which part should be clarified in the docs? #10445 clarifies things a bit.

[lgalfaso]

@Kamilius the way ISO-8601 handles the week number causes too may issues and there are many parts that are difficult for people to make sense. Eg.

• If the patter does not have the week token, then all is good and every day belongs to the same day/month/year that everybody expect.
• If the pattern has week, but it does not have day of the month (not day of the week) nor month, then (again) all is good
• If the pattern has week (and it may include year) and does not contain month nor day of the month then all the days within a week belong to the same week (even at the end of the year). This is, if in a given year Dec 31 is a Wednesday, then this Wednesday will be on W01 of the following year. On the other hand, if Dec 31 is a Thursday, then Friday that week will be on the same year than the Thursday

This is why if you are looking into a filter that is fully ISO-8601 compilant, then I would create a new external module that handles all these quirks. I looked at http://ngmodules.org/ to see if anybody already created one and was not able to find one

[pkozlowski-opensource]

@lgalfaso is right. I think that the only thing we miss is the info about the first day of a week in locale files as this varies from country to country.

[Kamilius]

@pkozlowski-opensource @lgalfaso #10445 is great, and yeah, thanks for all of the clarification.

[lgalfaso]

I would like to close this issue, but will keep it open for a few days in case someone wants to comment on it. The only way to really fix this would be to:

• Follow ISO-8601 definition of week number
• Add ISO-8601 week year (this would be used when used in a pattern that uses week number)

BTW, if someone is willing to create a PR, I think that it would be a better starting point to have this discussion

[pkozlowski-opensource]

@lgalfaso I think we can close this issue after #10445 landed with all the clarifications. I strongly believe that it doesn't make sense to implement ISO-860-way of determining week no - it has little practical value for web apps IMO.

What we should do instead is to keep the current algorithm and either allow people to specify the first day of a week (this varies by locale) or pull this info from locale files (this would be a new feature)

[pkozlowski-opensource]

So either we keep this issue to implement "specify a first day of a week" feature or close this one and open a separate issue for this new feature.

[lgalfaso]

ok, thanks