@andrew Seems to be a server thing. When creating an event for 15 Apr 2018 18:30:00 (Hong Kong), DAVdroid sends this event to the server:
BEGIN:VEVENT
DTSTAMP:20180415T101259Z
UID:1961cf67-bd19-4be9-abaf-8ab6e4aa7d7b
SUMMARY:Test
DTSTART;TZID=Asia/Hong_Kong:20180415T183000
DTEND;TZID=Asia/Hong_Kong:20180415T193000
STATUS:CONFIRMED
END:VEVENT
BEGIN:VTIMEZONE
TZID:Asia/Hong_Kong
TZURL:http://tzurl.org/zoneinfo/Asia/Hong_Kong
X-LIC-LOCATION:Asia/Hong_Kong
BEGIN:STANDARD
TZOFFSETFROM:+073642
TZOFFSETTO:+0800
TZNAME:HKT
DTSTART:19041030T000000
RDATE:19041030T000000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+0800
TZOFFSETTO:+0900
TZNAME:HKST
DTSTART:19410401T033000
RDATE:19410401T033000
RDATE:19460420T033000
RDATE:19470413T033000
RDATE:19480502T033000
RDATE:19490403T033000
RDATE:19500402T033000
RDATE:19510401T033000
RDATE:19520406T033000
RDATE:19530405T033000
RDATE:19540321T033000
RDATE:19550320T033000
RDATE:19560318T033000
RDATE:19570324T033000
RDATE:19580323T033000
RDATE:19590322T033000
RDATE:19600320T033000
RDATE:19610319T033000
RDATE:19620318T033000
RDATE:19630324T033000
RDATE:19640322T033000
RDATE:19650418T033000
RDATE:19660417T033000
RDATE:19670416T033000
RDATE:19680421T033000
RDATE:19690420T033000
RDATE:19700419T033000
RDATE:19710418T033000
RDATE:19720416T033000
RDATE:19730422T033000
RDATE:19731230T033000
RDATE:19750420T033000
RDATE:19760418T033000
RDATE:19790513T033000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:+0900
TZOFFSETTO:+0800
TZNAME:HKT
DTSTART:19410930T033000
RDATE:19410930T033000
RDATE:19450915T000000
RDATE:19461201T033000
RDATE:19471230T033000
RDATE:19481031T033000
RDATE:19491030T033000
RDATE:19501029T033000
RDATE:19511028T033000
RDATE:19521025T033000
RDATE:19531101T033000
RDATE:19541031T033000
RDATE:19551106T033000
RDATE:19561104T033000
RDATE:19571103T033000
RDATE:19581102T033000
RDATE:19591101T033000
RDATE:19601106T033000
RDATE:19611105T033000
RDATE:19621104T033000
RDATE:19631103T033000
RDATE:19641101T033000
RDATE:19651017T033000
RDATE:19661016T033000
RDATE:19671022T033000
RDATE:19681020T033000
RDATE:19691019T033000
RDATE:19701018T033000
RDATE:19711017T033000
RDATE:19721022T033000
RDATE:19731021T033000
RDATE:19741020T033000
RDATE:19751019T033000
RDATE:19761017T033000
RDATE:19791021T033000
END:STANDARD
BEGIN:STANDARD
TZOFFSETFROM:+0800
TZOFFSETTO:+0900
TZNAME:JST
DTSTART:19411225T000000
RDATE:19411225T000000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:+0900
TZOFFSETTO:+0900
TZNAME:HKST
DTSTART:19740421T033000
RDATE:19740421T033000
END:DAYLIGHT
END:VTIMEZONE
The DST definitions are until 1979 only (when the DST has been eliminated in Hong Kong Time). So the given offset is +0800, so DTSTART;TZID=Asia/Hong_Kong:20180415T183000
is equivalent to 20180415T103000Z
(10:30 UTC).
However, the server immediately rewrites the event to
BEGIN:VEVENT
DTSTART:20180415T093000Z
DTEND:20180415T103000Z
DTSTAMP:20180415T101313Z
UID:1961cf67-bd19-4be9-abaf-8ab6e4aa7d7b
CREATED:20180415T101259Z
LAST-MODIFIED:20180415T101259Z
SUMMARY:Test
CLASS:PUBLIC
STATUS:CONFIRMED
TRANSP:OPAQUE
END:VEVENT
As you can see, the server uses DTSTART:20180415T093000Z
which is
- without time zone information,
- at 9:30 UTC instead of 10:30 UTC.
See also https://bugs.horde.org/ticket/13866 (cPanel is using Horde, as far as I know).
Can you please report this to cPanel (guess it would be good to provide a link to this thread) and share the report URL here for tracking?