weekOfYear week edge cases with 2015-12-28 and 2016-10-30

[kwypchlo]

Describe the bug
weekOfYear week edge cases do not match moment week calculations

expect(dayjs('2015-12-28').week()).toBe(moment('2015-12-28').week())
// dayjs: 1 , moment: 53

expect(dayjs('2016-10-30').week()).toBe(moment('2016-10-30').week())
// dayjs: 44, moment: 43

Expected behavior
dayjs should return correct week of year, according to http://www.whatweekisit.org/ moment is correct

Information

• Day.js Version [1.8.19]
• OS: [Mac OS]
• Browser [running as unit test on Node 12.14.0]
• Time zone: [CET]

[iamkun]

🎉 This issue has been resolved in version 1.8.20 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[kwypchlo]

@iamkun this one is still not working properly, 1.8.20 did not fix it

[iamkun]

It should be fixed.

the test date, version, and locale, please?

[kwypchlo]

@iamkun it's current version "dayjs": "^1.8.20"

dayjs@^1.8.20:
  version "1.8.20"
  resolved "https://ui.nexus.crint.net/repository/npm-proxy/dayjs/-/dayjs-1.8.20.tgz#724a5cb6ad1f6fc066b0bd9a800dedcc7886f19e"
  integrity sha512-mH0MCDxw6UCGJYxVN78h8ugWycZAO8thkj3bW6vApL5tS0hQplIDdAQcmbvl7n35H0AKdCJQaArTrIQw2xt4Qg==

> dayjs.locale()
'en'

> dayjs.utc('2015-12-28T18:59:32').week()
1 // should be 53

dayjs.utc('2016-10-30T09:03').week()
45 // should be 43

[iamkun]

@kwypchlo test with moment.js and got the same result https://runkit.com/embed/5bhn5xbhf6ks
Maybe you should use the correct locale that week starting at monday

[kwypchlo]

@iamkun you are right, sorry for the confusion! Thank you for your work!

[4rno]

Hi,
I still an issue with the week() method compared with the moment.js one.
Here is an example of what moment.js week() method return for fr and en-gb locales.

I tried with that date: 2020-12-31, which is supposed to be a day in the week number 53. (if i refer to this http://www.whatweekisit.org/ or any french calendar)

moment.js returns week 53 : https://runkit.com/4rno/5f05ee0eef35c50013368d1b

I have different results with dayjs: https://runkit.com/4rno/5f05ebfc841930001389a53e
In fr locale, it returns week number 1. But in en-gb it returns correctly week 53.

It seems to be linked with the parameter yearStart in locale config files. But i don't know exactly how it is supposed to work.

Maybe i'm wrong somewhere.