.ics file exported from Reminders.app on OSX, with a few comments and examples of each of the fields.

Remindersapp_Export.ics

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Apple Inc.//Mac OS X 10.9.3//EN
CALSCALE:GREGORIAN

X-COMMENT: Copy your timezone data from an exported .ics file from Reminders.app.
BEGIN:VTIMEZONE
TZID:America/Denver
BEGIN:DAYLIGHT
TZOFFSETFROM:-0700
RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=2SU
DTSTART:20070311T020000
TZNAME:MDT
TZOFFSETTO:-0600
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0600
RRULE:FREQ=YEARLY;BYMONTH=11;BYDAY=1SU
DTSTART:20071104T020000
TZNAME:MST
TZOFFSETTO:-0700
END:STANDARD
END:VTIMEZONE

X-COMMENT: Your tasks begin here.
BEGIN:VTODO
STATUS:NEEDS-ACTION
DTSTAMP:20140526T161453Z
SEQUENCE:0
CREATED:20140526T161621Z
SUMMARY:Fake task with reminder leaving a location
UID:FCC6D666-82F3-42A1-B395-56607338A037
BEGIN:VALARM
X-WR-ALARMUID:AC85BC68-8E5B-4FAB-8D36-84349B754932
UID:AC85BC68-8E5B-4FAB-8D36-84349B754932
TRIGGER;VALUE=DATE-TIME:19760401T005545Z
ACTION:DISPLAY
X-APPLE-PROXIMITY:DEPART
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-APPLE-RADIUS=100;X-TITLE=350 Fif
 th Avenue New York NY 10118 United States:geo:40.748452,-73.985595
DESCRIPTION:Event reminder
END:VALARM
END:VTODO

BEGIN:VTODO
STATUS:NEEDS-ACTION
DTSTAMP:20140526T161318Z
SEQUENCE:0
CREATED:20140526T161318Z
SUMMARY:Fake task
UID:7B7A33C4-47FF-4DF8-BC36-96D2D457E07E
END:VTODO

BEGIN:VTODO
STATUS:NEEDS-ACTION
CREATED:20140526T161320Z
UID:4705531B-591B-4482-8269-460004E9EA9B
SUMMARY:Fake task with note
DTSTAMP:20140526T161320Z
SEQUENCE:0
DESCRIPTION:Fake task with note’s note
END:VTODO

BEGIN:VTODO
STATUS:NEEDS-ACTION
CREATED:20140526T161339Z
UID:A6D948F7-8398-478D-BD40-732F2CF7BB6A
SUMMARY:Fake task with reminder at 2015-12-31 at 3 PM
DTSTART;TZID=America/Denver:20151231T150000
DTSTAMP:20140526T161339Z
SEQUENCE:0
DUE;TZID=America/Denver:20151231T150000
BEGIN:VALARM
X-WR-ALARMUID:0CDDA7C7-6A8C-4CF4-AC4A-BB667C156FE9
UID:0CDDA7C7-6A8C-4CF4-AC4A-BB667C156FE9
TRIGGER;VALUE=DATE-TIME:20151231T220000Z
DESCRIPTION:Event reminder
ACTION:DISPLAY
END:VALARM
END:VTODO

BEGIN:VTODO
STATUS:NEEDS-ACTION
DTSTAMP:20140526T161453Z
SEQUENCE:0
CREATED:20140526T161453Z
SUMMARY:Fake task with reminder arriving at a location
UID:3F8C2F4F-D3A8-4E7F-BFF6-322B78096A55
BEGIN:VALARM
X-WR-ALARMUID:AC85BC68-8E5B-4FAB-8D36-84349B754932
UID:AC85BC68-8E5B-4FAB-8D36-84349B754932
TRIGGER;VALUE=DATE-TIME:19760401T005545Z
ACTION:DISPLAY
X-APPLE-PROXIMITY:ARRIVE
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-APPLE-RADIUS=100;X-TITLE=350 Fif
 th Avenue New York NY 10118 United States:geo:40.748452,-73.985595
DESCRIPTION:Event reminder
END:VALARM
END:VTODO

BEGIN:VTODO
STATUS:NEEDS-ACTION
CREATED:20140526T161637Z
UID:E2ECC838-FB0D-404F-A99A-C1A900CD1A41
SUMMARY:Fake task with medium priority
PRIORITY:5
DTSTAMP:20140526T161637Z
SEQUENCE:0
END:VTODO

X-COMMENT: Don't forget to add this on the end.
END:VCALENDAR