I have the recurring event show below, which properly displays the event on 7/29 in the Apple clients, Thunderbird, and Google's web app, but CalDAVZap doesn't show an event on 7/29.
BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Apple Inc.//Mac OS X 10.8.4//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:America/New_York BEGIN:DAYLIGHT TZOFFSETFROM:-0500 RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3 DTSTART:20070311T020000 TZNAME:EDT TZOFFSETTO:-0400 END:DAYLIGHT BEGIN:STANDARD TZOFFSETFROM:-0400 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11 DTSTART:20071104T020000 TZNAME:EST TZOFFSETTO:-0500 END:STANDARD END:VTIMEZONE BEGIN:VEVENT TRANSP:OPAQUE DTEND;TZID=America/New_York:20130708T100000 UID:8aecjj8jktg5ham42ag2bpb4no@google.com DTSTAMP:20130718T182134Z STATUS:CONFIRMED SEQUENCE:0 SUMMARY:Driver Ed LAST-MODIFIED:20130602T123428Z DTSTART;TZID=America/New_York:20130708T070000 CREATED:20130602T123428Z RRULE:FREQ=WEEKLY;UNTIL=20130729T110000Z;BYDAY=MO,TU,WE,TH,FR BEGIN:VALARM X-WR-ALARMUID:692B65FB-C722-47C6-9C27-E8F071D1C64C UID:692B65FB-C722-47C6-9C27-E8F071D1C64C TRIGGER;VALUE=DATE-TIME:19760401T005545Z X-APPLE-DEFAULT-ALARM:TRUE ACTION:NONE END:VALARM END:VEVENT END:VCALENDAR