If you would like to lookup a year span greater than 4 years, the returned events would be trimmed by the system to those from the first 4 years. (see Apple's documentation). What could be a possible solution is to run the predicate matching in batches.
Here's a C# extension for Xamarin.iOS
public static class EKEventStoreExtensions
{
private const int MaxPredicateYearSpan = 4;
public static EKEvent[] GetAllEvents(this EKEventStore eventStore, DateTimeOffset startAt, DateTimeOffset endAt, params EKCalendar[] calendars)
{
var isBatched = endAt.Year - startAt.Year >= MaxPredicateYearSpan;
var result = new List<EKEvent>();
var batchStartAt = startAt;
var batchEndAt = endAt;
while (batchStartAt < endAt)
{
if (isBatched)
{
batchEndAt = batchStartAt.AddYears(1);
if (batchEndAt > endAt)
{
batchEndAt = endAt;
}
}
var events = GetEventsMatching(eventStore, batchStartAt, batchEndAt, calendars);
result.AddRange(events);
batchStartAt = batchEndAt;
}
return result.ToArray();
}
private static EKEvent[] GetEventsMatching(EKEventStore eventStore, DateTimeOffset startAt, DateTimeOffset endAt, EKCalendar[] calendars)
{
var startDate = (NSDate)startAt.LocalDateTime;
var endDate = (NSDate)endAt.LocalDateTime;
var fetchCalendarEvents = eventStore.PredicateForEvents(startDate, endDate, calendars);
return eventStore.EventsMatching(fetchCalendarEvents);
}
}