Day manipulation (add and subtract) methods don't work properly after extension. They reset the date to 1970-01-01.

I've created a sandbox to reproduce the issue here.

Version: 2.2.2

According to the following lines I believe Utils object keys aren't really correct. But I don't have any ideas about why this works in the tests.

https://github.com/iamkun/dayjs/blob/dev/src/index.js#L43
https://github.com/iamkun/dayjs/blob/dev/src/utils.js#L45

Thanks for this lib.
but it seems there isn't any type definition for typescript types because when I use dayjs.calendar(...):

Property 'calendar' does not exist on type 'typeof import(".../node_modules/dayjs/index.d.ts")'.

I think you should extend the default dayjs's type definitions.

Hello @pi0
Please add more doc for jalaliday
And
Do not be tired ....

When I pass 2025/03/20, It gives back "1404/1/1" and it's wrong. It should return "1403/12/30"

hi,
When I want to change the date, the date is converted as follows and the same jalali date is returned

1400/05/07 => Thu May 08 1400 00:00:00 GMT+0325 (Iran Daylight Time)

const date = "1400/05/07"
dayjs(date ).calendar("gregory").locale("en")

how i can convert jalali date to gregory ?

Please consider the sample:

import dayjs from 'dayjs';
import jalaliday from 'jalaliday';

dayjs.extend(jalaliday);
dayjs.calendar('jalali');

const date = dayjs('1367/02/23', { jalali: true })
const gregory = date.calendar('gregory')
const jalaliDate = date.calendar('jalali');

// Should be 1367/02/23, but is 1367/1/23
console.log(jalaliDate.year() + "/" + jalaliDate.month() +"/"+ jalaliDate.date()); 

 // Should be 1988/05/13, but is 1988/4/13
console.log(gregory.year() + "/" + gregory.month() +"/"+ gregory.date());

This library calculates the conversion of dates incorrectly.

Changing the dayjs calendar for all instance doesn't work.

In the $set method, the $d property is being updated in this order:

1. setDate
2. setMonth
3. setFullYear

It causes unexpected results in certain cases like this one:

// 2019-11-01
dayjs('1398-08-10', { jalali: true })
  .calendar('jalali')
  .date(9)

The results should be 1398-08-09 but it becomes 1398-07-09. This happens because setDate is called first. Which depends on the current month value and if the given date exceeds the limit of that month, it goes to the next one.

We should reverse the order so that setDate can be aware of the new month value.

when I try to use jalaliday in a specific component I realize it converts my Jalali year 1399 to gregorian 3263 instead of 2020.
as I check more I find out its a combination of webpack and your library problem.
when someone import jalalidate in multiple modules in one special hierarchy and extend the original dayjs this library keep adding extra year in date convert process for example if I use this:

import dayjs from 'dayjs';
import jalaliday from 'jalaliday';
dayjs.extend(jalaliday);
dayjs.extend(jalaliday);
dayjs.extend(jalaliday);

the final result of dayjs(1399-08-08, { jalali: true }); will be 4505
as you add more extend it add 621 years to the resulting year
3263->3884->4505->....
i think there must be a solution that multiple extend won't result in wrong date convert

Hi there,

Just a quick reminder that there are two changes in 1.8.9 to our developers.

1. Date wrapper Utils.wrapper could be overridden in the plugin.

2. The name of Utiles[*] has been changed to a shorter name in order to reduce the package size.

Cheers.

Currently what you get out of months() method is dependant on locale which is wrong.
It should depend on calendar, and locale should only define the language:

dayjs.locale('fa')
console.log(dayjs.calendar('jalali').months())
// outputs: ['فروردین', 'اردیبهشت', 'خرداد', 'تیر', 'مرداد', 'شهریور', 'مهر', 'آبان', 'آذر', 'دی', 'بهمن', 'اسفند']
// Correct!
console.log(dayjs.months())
// outputs: ['فروردین', 'اردیبهشت', 'خرداد', 'تیر', 'مرداد', 'شهریور', 'مهر', 'آبان', 'آذر', 'دی', 'بهمن', 'اسفند']
// Wrong! It should be ژانویه فوریه مارچ etc.

dayjs.locale('en')
console.log(dayjs.calendar('jalali').months())
// outputs: ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
// Wrong! It should be Farvardin, Ordibehesht, etc.
console.log(dayjs.months())
// outputs: ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
// Correct!

وقتی ماه رو تنظیم میکنم برای ماه 12 دچار اشکال میشه.
`
dayjs().calendar('jalali').locale('fa').month(11).format('MMMM'); // فروردین
dayjs().calendar('jalali').locale('fa').month(0).format('MMMM'); // فروردین

dayjs().calendar('jalali').locale('fa').date(1).month(11).format('MMMM'); // اسفند
`

when I use time zone .tz() function , it converted to georgian

endOf and daysInMonth functions don't work when they are called inside the Esfand month of years with no extra leap day.

This library shows Esfand month 1403 as 29 days, which is actually a 30-day month but This shows Esfand month 1404 as 30.

امسال با توجه به اینکه ساعت را عقب نکشیدن ساعت خروجی عبارت زیر اشتباه بر می گردد.

dayjs(2023-04-10T10:19:56+0430).calendar('jalali').locale('fa').format('HH:mm - YYYY/MM/DD')
نتیجه
09:19 - 1402/01/21

Hi,
I found out that this library uses an incorrect method for calculating leap years,
As an example:
This library shows Esfand month 1403 as 29 days, which is actually a 30-day month.
Additionally, I checked the jalaali-js library and found that it is calculating leap years correctly.

Demo:
https://js-r3ebqv.stackblitz.io

Correct:

Note:

List of leap years (problem is with the leap before the five-year leap)
As an example, the year 1408 is a five-year leap, and the leap before this year is 1403. or the year 1441 is a five-year leap, and the leap before this year is 1436.
There is no support for five-year leap years in this plugin, and all leap years are based on four-year leap years.

KabiseShamsi1206-1498-new.pdf

Date of month is wrong in some months

Example for Bahman (1399/11/11):

const date = dayjs().calendar('jalali').locale('fa');
console.log('days =', date.daysInMonth());
for (let i = 1; i <= date.daysInMonth(); i++) {
    console.log('day ' + (i < 10 ? '0' : '') + i + 'th = ' + date.format('DD'));
}

Output: