[Bug Report][3.7.4] Wrong number week with locale-provider "fr"

[SamsGuamejy]

Environment

Vuetify Version: 3.7.4
Vue Version: 3.5.13
Browsers: Firefox 128.0, Google Chrome
OS: Windows 10

Steps to reproduce

When I use the v-locale-provider with "fr" around the v-date-picker, the weekNumber for the first week of 2025, the date-picker write the week 53.
The weekNumber will be week 01 for the December 30, 2024 to January 5, 2025.

Expected Behavior

Display the week 01 for the December 30, 2024 to January 5, 2025. ISO 8601 right

Actual Behavior

Display the weekNumber 53 for the December 30, 2024 to January 5, 2025.

Reproduction Link

Original Playground

Playground for v3.8.0

[SamsGuamejy]

@MatthewAry :Can you tell me if this issue can be definded like a bug?
Thank you.

[SamsGuamejy]

First week
The ISO 8601 definition for week 01 is the week with the first Thursday of the Gregorian year (i.e., of January) in it. The following definitions based on properties of this week are mutually equivalent, since the ISO week starts with Monday:

It is the first week with a majority (4 or more) of its days in January.
Its first day is the Monday nearest to 1 January.
It has 4 January in it. Hence the earliest possible first week extends from Monday 29 December (previous Gregorian year) to Sunday 4 January, the latest possible first week extends from Monday 4 January to Sunday 10 January.
It has the year's first working day in it, if Saturdays, Sundays and 1 January are not working days.
If 1 January is on a Monday, Tuesday, Wednesday or Thursday, it is in W01. If it is on a Friday, it is part of W53 of the previous year. If it is on a Saturday, it is part of the last week of the previous year which is numbered W52 in a common year and W53 in a leap year. If it is on a Sunday, it is part of W52 of the previous year.

[MatthewAry]

I will mark this a bug and bring this to the attention to other members of the team because I don't know what commitment has been made to sticking to the ISO 8601 spec. I do note that the VDatePicker uses date-io and the native date object in it's logic. I also note that there is explicit support for internationalization by mounting custom date adapters to the root createVuetify method.

[SamsGuamejy]

Thx @MatthewAry !

[simon-tackstrand]

We have the same issue. This means that all weeks for 2025 currently is off by one week in the date-picker.

It seems to be a bug in the getWeek() implementation as described here #20490 vuetify.

Rather than vuetify using its own implementation the adapters instance week implementation should be used i.e. dayjs('2024-12-30').week() which returns the correct localized week. However, the date-io adapter interface does not seem to have support for week number which is mentioned here #644 date-io