Under TYPO3 Version 8.7.0, start and end time of events become 4 hours less after saving.
If I e.g. enter 00:00 into field "start time", it becomes 20:00 after pressing save.
If I press the save button again, it become 18:00 (2 hours less), next time 16:00 and so on.
The problem also exists at the datetime field "start" under tab "access" of calendar records,
but neither in records of other extensions e.g. news nor in content elements.
I thing the problem stock somewhere inside the IndexPreperationService method prepareRecordForDatabase.
If I e.g. enter 00:00 into start time field and press save, this value becomes 1491422400 inside $record['start_time'], which correspond to 05.04.2017 22:00:00 in local time and 05.04.2017 20:00:00 in utc. Apart of the date this ist exactly the value I see after page reloads.
I thing in general, the value of "start_time" and "end_time" should not be greater than 86400 (because time) at this place. But if I look in the database table "tx_calendarize_domain_model_index", all values are greater, beside some "end_date" values, which I leave empty.
If I look into the database of an other TYPO3 installation, but Version 7.6, all values are smaller than 86400.