Hideyuki Takeuchi

dayjs('2020-10-01').add(dayjs.duration(1, 'months')) not returns dayjs('2020-11-01')

3

**Describe the bug** `dayjs.duration(1, 'months')` is converted to `dayjs.duration(30, 'days')` internally by duration plugin. so `dayjs('2020-10-01').add(dayjs.duration(1, 'months'))` returns `dayjs('2020-10-31')` **Expected behavior** `dayjs('2020-10-01').add(dayjs.duration(1, 'months'))` should returns `dayjs('2020-11-01')` **Information** - Day.js Version:...

fix: Duration.constructor()/toISOString()/add()/subtract() does not work properly

7

Fixes #1515 Fixes #1516 **This PR is fixing two issues.** - Duration.constructor()/toISOString() does not work properly with negative value ISO String - Duration.add()/subtract() does not work properly with adding `dayjs.duration(1,...