When looking into the database table oc_calendars the timezone column entries seem to be wrong when they are not NULL.
The timezone is stored as a VCALENDAR event. To me this seems wrong and should instead be e.g. Europe/Berlin 
Can someone enlighten me before I open an issue?
NC Version: 22.2.3
Calendar Version: 3.0.5
MariaDB [nextcloud]> select * from oc_calendars;
+----+-------------------------------------------------------+-----------------------+-----------------------+-----------+-------------+---------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+-------------+------------+
| id | principaluri | displayname | uri | synctoken | description | calendarorder | calendarcolor | timezone | components | transparent | deleted_at |
+----+-------------------------------------------------------+-----------------------+-----------------------+-----------+-------------+---------------+---------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------+-------------+------------+
| 8 | principals/users/admin1 | Personal | personal | 1 | NULL | 0 | NULL | NULL | VEVENT,VTODO | 0 | NULL |
| 9 | principals/users/admin2 | Personal | personal | 1 | NULL | 0 | NULL | NULL | VEVENT,VTODO | 0 | NULL |
| 23 | principals/users/92F7ED71-5921-4FED-AD86-46812A23B841 | Arbeit | personal | 2495 | NULL | 0 | #0000ff | NULL | VEVENT,VTODO | 0 | NULL |
| 24 | principals/users/1778B28A-5292-46E8-A719-CAE94D811E38 | Personal | personal | 1370 | NULL | 0 | #3366cc | NULL | VEVENT,VTODO | 0 | NULL |
| 25 | principals/users/16AA02DE-C7B7-4AD5-A8A4-74D78D6E3B8D | Personal | personal | 11 | NULL | 0 | NULL | NULL | VEVENT,VTODO | 0 | NULL |
| 26 | principals/users/33272D4B-D720-496E-A1C6-D06511A3872B | Personal | personal | 78 | NULL | 0 | NULL | NULL | VEVENT,VTODO | 0 | NULL |
| 27 | principals/users/45D929D5-7C93-44C7-884A-15748A264AF2 | Personal | personal | 169 | NULL | 0 | NULL | NULL | VEVENT,VTODO | 0 | NULL |
| 28 | principals/users/B5A6A6EC-8E74-4CEC-BD26-A6C1C1640125 | Personal | personal | 178 | NULL | 0 | NULL | NULL | VEVENT,VTODO | 0 | NULL |
| 29 | principals/users/435CA138-C16F-4BA3-B663-5BFC8F4841B9 | Personal | personal | 897 | NULL | 5 | #ff2600FF | BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Apple Inc.//macOS 11.4//EN
CALSCALE:GREGORIAN
BEGIN:VTIMEZONE
TZID:Europe/Berlin
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
DTSTART:19810329T020000
TZNAME:MESZ
TZOFFSETTO:+0200
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
DTSTART:19961027T030000
TZNAME:MEZ
TZOFFSETTO:+0100
END:STANDARD
END:VTIMEZONE
END:VCALENDAR
| VEVENT,VTODO | 0 | NULL |
| 30 | principals/users/ABC | ABC-Geburtstage | geburtstage | 61 | NULL | 0 | #d9e255 | BEGIN:VCALENDAR
PRODID:-//IDN nextcloud.com//Calendar app 2.0.3//EN
CALSCALE:GREGORIAN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:Europe/Berlin
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19700329T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19701025T030000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
END:STANDARD
END:VTIMEZONE
END:VCALENDAR | VEVENT | 0 | NULL |
| 31 | principals/users/ABC | ABC-Abwesenheit | abwesenheit | 3139 | NULL | 0 | #D6B461 | BEGIN:VCALENDAR
PRODID:-//IDN nextcloud.com//Calendar app 2.0.3//EN
CALSCALE:GREGORIAN
VERSION:2.0
BEGIN:VTIMEZONE
TZID:Europe/Berlin
BEGIN:DAYLIGHT
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:19700329T020000
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
TZNAME:CET
DTSTART:19701025T030000
RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
END:STANDARD
END:VTIMEZONE
END:VCALENDAR | VEVENT | 0 | NULL |
| 32 | principals/users/7D1CB51E-C7A9-4B40-9228-29B1ABDAFAA7 | Personal | personal | 8 | NULL | 0 | NULL | NULL | VEVENT,VTODO | 0 | NULL |
| 33 | principals/users/EA3C5C4B-F5A2-4BA9-9E7D-64BEBE2AD000 | Personal | personal | 15 | NULL | 0 | NULL | NULL