Objective-C: Get the number of calendar days between two dates - objective-c

Question

I just don't get the correct result...so depending on the timezone I want the calendar day difference between two dates. So if one starts at 23:00 on day 1 and ends on 14:00 on day 2 it should return 1. Now my method returns 0, why? Because it's less than 24 hours? Example:
MY Nslog:
CheckForPictures departure date: Tue Jan 28 23:10:00 2020 destinationDate: Wed Jan 29 09:30:00 2020 in timeZone:Europe/Zurich and get a day difference: 0
(Computer has also timezone Zurich, so it is local time)
My Method:
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar setTimeZone:timeZone];
NSDateComponents *components = [calendar components:NSCalendarUnitDay
fromDate:self.departureTime
toDate:self.destinationTime
options:0];
NSLog(#"CheckForPictures departure date: %# destinationDate: %# in timeZone:%# and get a day difference: %ld", self.departureTime, self.destinationTime, timeZone.name, components.day);
return components.day;
And this code returns 0 and logs above log...

Answer 1

I believe you're asking NSCalendar the wrong question. You want to know if the arrival date is different than the departure date, but you're asking for the number of days between arrival and departure. A date change could happen even if the difference in time is only a few minutes. "A few minutes" rounds to "0 days" if you ask how many days have passed.
You actually want to know if the date has changed. I think I would be doing something like getting the day of the month for each date and comparing that. Since no months have 1 day, I would think that would work.

Answer 2

With Craigs input I came up with this solution:
- (NSInteger)calendarDaysBetweenDepartureAndArrivalTimeForTimeZone:(NSTimeZone *)timeZone
{
NSCalendar *calendar = [NSCalendar currentCalendar];
[calendar setTimeZone:timeZone];
NSDateComponents *departureComponents = [calendar components:(NSCalendarUnitDay) fromDate:self.departureTime];
NSDateComponents *destinationComponents = [calendar components:(NSCalendarUnitDay) fromDate:self.destinationTime];
NSInteger difference = destinationComponents.day - departureComponents.day;
if(difference < 0){
//Month overlapping
NSRange range = [calendar rangeOfUnit:NSCalendarUnitDay inUnit:NSCalendarUnitMonth forDate:self.departureTime];
difference = range.length - departureComponents.day + departureComponents.day;
}
NSLog(#"CheckForPictures departure date: %# destinationDate: %# in timeZone:%# and get a day difference: %ld", self.departureTime, self.destinationTime, timeZone.name, difference);
return difference;
}