Number of days between two NSDate objects

Question

I'm trying to compare two days of NSDate objects, I used at the first time NSDateComponents to calculate difference between my two dates Objects, but it is working correctly.

    NSString *dateStr =@"2012-11-05 15:00:00";
    NSDate *date = [dateFormat dateFromString:dateStr];
    NSDateComponents *datesDiff = [calendar components: NSDayCalendarUnit
                                              fromDate: date
                                                toDate: [NSDate date]
                                               options: 0];

That does not resolve my problem. Indeed when date1 = 2012-11-05 23:00:00 and date2 = 2012-11-06 10:00:00, the difference between the tow dates is 0 day and 11 hours. I am looking for something that allows me to detect day changes, in other words when date1 = 2012-11-05 23:00:00 and date2 = 2012-11-06 00:01:00, there's one day diffrence.

If someone knows the solution for that, i would welcome his suggestion. Thanks in advance

Answer 1

I think you are looking for this (from the Date and Time Programming Guide):

Listing 13 Days between two dates, as the number of midnights between

@implementation NSCalendar (MySpecialCalculations)

-(NSInteger)daysWithinEraFromDate:(NSDate *) startDate toDate:(NSDate *) endDate
{
     NSInteger startDay=[self ordinalityOfUnit:NSDayCalendarUnit
          inUnit: NSEraCalendarUnit forDate:startDate];
     NSInteger endDay=[self ordinalityOfUnit:NSDayCalendarUnit
          inUnit: NSEraCalendarUnit forDate:endDate];
     return endDay-startDay;
}
@end

EDIT: Swift version:

extension NSCalendar {
    func daysWithinEraFromDate(startDate: NSDate, endDate: NSDate) -> Int {
        let startDay = self.ordinalityOfUnit(.Day, inUnit: NSCalendarUnit.Era, forDate: startDate)
        let endDay = self.ordinalityOfUnit(.Day, inUnit: NSCalendarUnit.Era, forDate: endDate)
        return endDay - startDay
    }
}

Answer 2

NSString *start = @"2010-09-01";
NSString *end = @"2010-12-01";

NSDateFormatter *f = [[NSDateFormatter alloc] init];
[f setDateFormat:@"yyyy-MM-dd"];
NSDate *startDate = [f dateFromString:start];
NSDate *endDate = [f dateFromString:end];
[f release];

NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [gregorianCalendar components:NSDayCalendarUnit
                                                    fromDate:startDate
                                                      toDate:endDate
                                                     options:0];
[gregorianCalendar release];

components now holds the difference.

NSLog(@"%ld", [components day]);

Answer 3

func daysBetweenDates(startDate: NSDate, endDate: NSDate) -> Int
{
    let calendar = NSCalendar.currentCalendar()

    let components = calendar.components([.Day], fromDate: startDate, toDate: endDate, options: [])

    return components.day
}

or

let calendar = NSCalendar.currentCalendar();
let component1 = calendar.component(.Day, fromDate: fromDate)
let component2 = calendar.component(.Day, fromDate: toDate)
let difference  = component1 - component2

Answer 4

For Swift 3:

Expanding from @masa's answer:

extension Calendar {
    func daysWithinEraFromDate(startDate: Date, endDate: Date) -> Int? {
        guard let startDay = ordinality(of: .day, in: .era, for: startDate) else {
            return nil
        }

        guard let endDay = ordinality(of: .day, in: .era, for: endDate) else {
            return nil
        }

        return endDay - startDay
    }
}