EKEventStore time zone isn't GMT - objective-c

Question

I'm trying to retrieve all the events for a single day from an instance of EKEventStore using eventsMatchingPredicate:, but as I read, the NSDate objects are by default set to GMT while the EKEventStore isn't. So my question is how do I change the timezone of the EKEventStore or adjust the NSDate objects so that the times aren't off for each timezone?
For example, I'm in GMT -0600, and clicking on January 16th and 17th in the TKCalendarMonthView I'm using for a calendar UI shows Martin Luther King Day on both dates. The start time is 6 AM on 16 January, and the end time is 5:59 AM on 17 January (as a result of my timezone), rather than beginning at 12:00 AM and lasting until 11:59 PM. The code used to retrieve events follows.
- (void)calendarMonthView:(TKCalendarMonthView *)monthView didSelectDate:(NSDate *)d {
// Update tableData with event data from date
[tableData removeAllObjects];
NSArray *a = [systemCalendar eventsMatchingPredicate:[systemCalendar predicateForEventsWithStartDate:d endDate:[NSDate dateWithTimeInterval:84600 sinceDate:d] calendars:nil]];
[tableData addObjectsFromArray:a];
[self.eventsTable reloadData];
}

Answer 1

Given that I'm on a short timeline, I came up with a solution, and it seems to work. My only concern is that I had to multiply the offset by -1 even though the time interval offset itself is negative. This doesn't make sense because we are trying to subtract from the NSDate rather than add to it. A positive number minus a negative number gives us a larger number, so I'm slightly worried about the GMT zones on the other side of the PM and wondering whether I should actually be multiplying all time intervals by -1. Anyone have any thoughts?
- (void)calendarMonthView:(TKCalendarMonthView *)monthView didSelectDate:(NSDate *)d {
[NSTimeZone resetSystemTimeZone];
NSTimeZone *tz = [NSTimeZone systemTimeZone];
NSArray *comps = [[tz description] componentsSeparatedByString:#" "];
NSTimeInterval offset = (NSTimeInterval)[[comps lastObject] floatValue];
if (offset < 0) {
offset *= -1;
}
NSDate *startDate = [d dateByAddingTimeInterval:offset];
NSArray *a = [systemCalendar eventsMatchingPredicate:[systemCalendar predicateForEventsWithStartDate:startDate endDate:[NSDate dateWithTimeInterval:84600 sinceDate:startDate] calendars:nil]];
NSLog(#"Events for the date: %#", a);
[tableData addObjectsFromArray:a];
[self.eventsTable reloadData];
}