Vue2-datepicker: [Bug] Wrong week number in 2021

[kugatsu765]

Vue2-datepicker version: 3.8.2
Vue version: 2.6.11
Browser: All

Steps to reproduce

• Display calendar with type="week"
• look the first week of 2021

Reproduction Link or Source Code

Expected behavior
The week number should be calculate by following ISO 8601
ISO 8601 wiki

The week number should be:

• 53 from 28 to 3
• 1 from 4 to 10
• 2 ...
• ....

Actual behavior
The week number is:

• 1 from 28 to 3
• 2 from 4 to 10
• 3 ...
• ....

PS
Thanks for your work and this great component.

[mengxiong10]

You can change the firstWeekContainsDate.

<date-picker  :lang="{ formatLocale: { firstWeekContainsDate: 4 } }" />

[kugatsu765]

Thank you =)

[janvince]

Thank you!