Non-valid .toISOString(), must include 'Z' at the end

[warmrobot]

https://github.com/date-fns/tz/blob/main/src/date/index.js#L29-L30

And there is no seconds, by the way

[GianlucaWassermeyer]

Hello,

The 'Z' indicates that the ISOString is in Zulu time (UTC). He uses the variant with the timezone offset inside the ISOString for TZDate, which is just as valid as the other format. Furthermore, JavaScript Date does not accept any timezone offsets with seconds; it would be an invalid ISOString.