ElementDateEditor cyclically transforms non UTC dates to UTC on every onChange()

[vbackeberg]

I believe there is an issue with the onChange() code in ElementDateEditor. If the browser timezone is not UTC, it will repeatedly change the timezone to UTC if you click the element.

Expected:
In the "Date and Time" element, after selecting the date field, deselecting it and then selecting it again, it will not change.

Observed:
In the "Date and Time" element, after selecting the date field, deselecting it and then selecting it again, it will transform the timezone to UTC once more.

Steps to reproduce:

1. Set any timezone except UTC
2. Add "Date and Time" form element and apply.
3. Select a date
4. Click outside the field to trigger onChange()

Fix:
Add timezone to the input date before calling toISOString()

[mikhail-vl]

@vbackeberg Thank you for submitting the issue. We will look into it and get back to you.