When uploading an event at 16 Feb 2017 10:00 Eastern standard time, DAVdroid puts this event + ical4j timezone definition to the server:
BEGIN:VCALENDAR VERSION:2.0 PRODID:+//IDN bitfire.at//DAVdroid/1.4.0.2 ical4android ical4j/2.x BEGIN:VEVENT DTSTAMP:20170219T175556Z UID:20170219T175554Z-b17c600e48506c59 DTSTART;TZID=America/New_York:20170216T100000 DTEND;TZID=America/New_York:20170216T110000 SUMMARY:Test STATUS:TENTATIVE END:VEVENT BEGIN:VTIMEZONE TZID:America/New_York TZURL:http://tzurl.org/zoneinfo/America/New_York X-LIC-LOCATION:America/New_York BEGIN:DAYLIGHT TZOFFSETFROM:-0500 TZOFFSETTO:-0400 TZNAME:EDT DTSTART:20070311T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 TZNAME:EST DTSTART:20071104T020000 RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU END:STANDARD END:VTIMEZONE END:VCALENDAR(empty lines for visual separation)
Then, Horde converts this to this and sends it back (as an updated event):
BEGIN:VCALENDAR VERSION:2.0 X-WR-CALNAME:Cal Of Thrones PRODID:-//The Horde Project//Horde iCalendar Library//EN BEGIN:VEVENT DTSTART;TZID=America/New_York:20170216T090000 DTEND;TZID=America/New_York:20170216T100000 DTSTAMP:20170219T175649Z UID:20170219T175554Z-b17c600e48506c59 CREATED:20170219T175634Z LAST-MODIFIED:20170219T175634Z SUMMARY:Test CLASS:PUBLIC STATUS:TENTATIVE TRANSP:OPAQUE END:VEVENT BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT TZOFFSETFROM:-0400 !!!! TZOFFSETTO:-0400 DTSTART:20070311T020000 RRULE:FREQ=YEARLY;BYMONTH=3;BYMONTHDAY=8,9,10,11,12,13,14;BYDAY=1SU TZNAME:EDT END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 TZOFFSETTO:-0500 DTSTART:20071104T020000 RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU TZNAME:EST END:STANDARD END:VTIMEZONE END:VCALENDARAs you can see, the daylight definition switches from a -4:00 offset to -4:00, while standard time switches from -4 to -5.
So this is a timezone problem of Horde (specifically in the DAYLIGHT definition) and not a DAVdroid problem. Please contact Horde regarding this.
I don’t know why SOGo has this problem, too. Maybe there’s a problem with the tzdata, but in this case, I can’t do anything, too.
If there are any indications that this could be a DAVdroid problem, feel free to post here again.