Scheduled webforms open/close date aren't converted to UTC before being stored in database.
When saving the node, the date will be formatted using WebformDateHelper::formatStorage(). In this method, no timezone is passed to $date->format(), leading to the date that was submitted in a local timezone being saved to the database directly (no tz conversion).
Passing the proper timezone to format()-call.
Closed: won't fix
6.2
Code
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.
Changing how dates are stored will cause regressions. It is probably best to leave dates AS-IS