Add this type of testing to `.toString()` ('should be serialize string which can be loaded by new Date') helps to cover corner cases and solve special cases such:
* Negative date time not being serialised correctly in the iso standard. Years should always have 6 digits and the signal in front for working correctly with negative years and high numbers. This also avoids the year 2000 problem. See, https://en.wikipedia.org/wiki/ISO_8601
* `Date.fromStandardDate` factory was not taking in consideration the `seconds` contribution in the timezone offset. This is not a quite common scenario, but there are dates with timezone offset of for example `50 minutes` and `20 seconds`.
* Fix `Date.toString` for dates with offsets of seconds. Javascript Date constructor doesn't create dates from iso strings with seconds in the offset. For instance, `new Date("2010-01-12T14:44:53+00:00:10")`. So, this tests should be skipped.

Add this type of testing to `.toString()` ('should be serialize string which can be loaded by new Date') helps to cover corner cases and solve special cases such:
* Negative date time not being serialised correctly in the iso standard. Years should always have 6 digits and the signal in front for working correctly with negative years and high numbers. This also avoids the year 2000 problem. See, https://en.wikipedia.org/wiki/ISO_8601
* `Date.fromStandardDate` factory was not taking in consideration the `seconds` contribution in the timezone offset. This is not a quite common scenario, but there are dates with timezone offset of for example `50 minutes` and `20 seconds`.
* Fix `Date.toString` for dates with offsets of seconds. Javascript Date constructor doesn't create dates from iso strings with seconds in the offset. For instance, `new Date("2010-01-12T14:44:53+00:00:10")`. So, this tests should be skipped.
Co-authored-by: Robsdedude <dev@rouvenbauer.de>