fix(datepicker): min-date validation is incorrect in GMT+X timezones

[Splaktar]

PR Checklist

Please check that your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added or this is not a bug fix / enhancement
• Docs have been added, updated, or were not required

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Enhancement
[ ] Documentation content changes
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Infrastructure changes
[ ] Other... Please describe:

What is the current behavior?

The datepicker's min-date validation is incorrect in GMT+X timezones. See issue for details.

Issue Number:
Fixes #11963

What is the new behavior?

The validation errors in GMT+X timezones are fixed.
Some JSDoc is fixed.

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

We don't have the capability to change the device's timezone between tests.