`dayjs.tz()` is not building dates with correct timezone for many cases

Describe the bug When you try to use dayjs.tz factory it isn’t providing the instance properly, even using some ISO formats and Date object string outputs.

Some examples using a UTC environment :

Input	Output	Expected
2022-03-11T14:29:26.319Z	2022-03-11T14:29:26-03:00	2022-03-11T11:29:26-03:00
Fri, 11 Mar 2022 14:29:26 GMT	2022-03-11T14:29:26-03:00	2022-03-11T11:29:26-03:00
3/11/2022, 2:29:26 PM	2022-03-11T14:29:26-03:00	2022-03-11T11:29:26-03:00
2014-02-03T16:50:21Z	2014-02-03T16:50:21-03:00	2014-02-03T13:50:21-03:00
2012-02-01T13:50:21.01-03:00	2012-02-01T16:50:21-03:00	2012-02-01T13:50:21-03:00
2022-02-03T13:50:21-00:00	2022-02-03T13:50:21-03:00	2022-02-03T10:50:21-03:00

The behavior is odd, for the Date input it fails sometimes but also should be accepted especially the ISO format native Date outputs.

Reproducible code:

https://gist.github.com/LeonanCarvalho/35d1596dcfb701255d04b93d70df69a0

Expected behavior Construct dayjs with correct timezone.

Information

• Day.js Version v1.10.8
• OS: [e.g. iOS]
• Browser: nodeJS v14.17.3
• Time zone: UTC (tests in UTC but also in GMT -3)

[hbj]

I was about to file a bug regarding dayjs.tz and found this one which seems related. The issue is that the function is not converting correctly between timezones. Simplest case to see is when converting to the same timezone is leading to the time to be changed!

Example:

dayjs.tz('2022-02-21 22:00', 'YYYY-MM-DD HH:mm', 'Europe/Paris').toISOString()
=> '2022-02-21T21:00:00.000Z'
dayjs.tz('2022-02-21 22:00', 'YYYY-MM-DD HH:mm', 'Europe/Paris').tz('Europe/Paris').toISOString()
=> '2022-02-21T22:00:00.000Z'

It seems to be applying the offset of the target timezone without taking into consideration the timezone of the original date!

[sevrai]

To date, I get the same result 2022-02-21T21:00:00.000Z in both cases dayjs: 1.11.5 macOS NodeJS: 16.13.1

I’ve got the same.

In my case, release 1.11.2 solved my problem.