dayjs duration Incorrect calculation

[15678871232]

Describe the bug
A clear and concise description of what the bug is.
const duration2023 = this.$dayjs.duration(this.$dayjs('2023-12-31 23:59:59').diff(this.$dayjs('2023-01-01 00:00:00')));
out: {
"years": 0,
"months": 12,
"days": 4,
"hours": 23,
"minutes": 59,
"seconds": 59,
"milliseconds": 0
}

const duration2024 = this.$dayjs.duration(this.$dayjs('2024-12-31 23:59:59').diff(this.$dayjs('2024-01-01 00:00:00')));
out: {
"years": 1,
"months": 0,
"days": 0,
"hours": 23,
"minutes": 59,
"seconds": 59,
"milliseconds": 0
}

years 0&&1
Expected behavior
A clear and concise description of what you expected to happen.
Consistent year
Information

• Day.js Version [v1.11.13]
• OS: [WIN 11]
• Browser [edge 128.0.2739.67 ]
• Time zone: [GMT-08:00 ]

[juliusv]

I think I'm seeing the same similar bug for converting a duration to either hours or days for anything larger than 30 days (it works until that point, breaks down after).

Here's a few simple test cases to reproduce where it breaks:

  // SUCCEEDS, it returns 29 days.
  it('convert just less than 30-something days to days', () => {
    expect(dayjs.duration((86400000 * 30) - 1).days()).toBe(29)
  })
  // FAILS, it returns 0 instead of 30 days.
  it('convert just less than 31-something days to days', () => {
    expect(dayjs.duration((86400000 * 31) - 1).days()).toBe(30)
  })
  // SUCCEEDS, it returns 23 hours.
  it('convert just less than 30-something days to hours', () => {
    expect(dayjs.duration((86400000 * 30) - 1).hours()).toBe(23)
  })
  // FAILS, it returns 13 instead of 23 hours.
  it('convert just less than 31-something days to hours', () => {
    expect(dayjs.duration((86400000 * 31) - 1).hours()).toBe(23)
  })

[juliusv]

Sorry, I wasn't dayjs-ing correctly. 30 is of course the number of days in a month, and months are separately extracted, and then 0 for the days makes sense. And then 13 for the hours comes from the fact that a month is not defined as exactly 30 days, but as const MILLISECONDS_A_MONTH = MILLISECONDS_A_YEAR / 12.

So please ignore my comment.