¿Cómo desgloso un NSTimeInterval en año, meses, días, horas, minutos y segundos en el iPhone?

Este código es consciente de los tiempos de ahorro de luz del día y otras posibles cosas desagradables.

NSCalendar *gregorianCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *components = [gregorianCalendar components: (NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit | NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit )
                                                    fromDate:startDate
                                                      toDate:[NSDate date]
                                                     options:0];


NSLog(@"%ld", [components year]);
NSLog(@"%ld", [components month]);
NSLog(@"%ld", [components day]);
NSLog(@"%ld", [components hour]);
NSLog(@"%ld", [components minute]);
NSLog(@"%ld", [components second]);

Desde iOS8 y superior puede usar NSDateComponentsFormatter

Tiene métodos para convertir la diferencia de tiempo en una cadena formateada fácil de usar.

NSDateComponentsFormatter *formatter = [[NSDateComponentsFormatter alloc] init];
formatter.unitsStyle = NSDateComponentsFormatterUnitsStyleFull;

NSLog(@"%@", [formatter stringFromTimeInterval:1623452]);

Esto da la salida-2 semanas, 4 días, 18 horas, 57 minutos, 32 segundos

Convierta su intervalo en un NSDate usando +dateWithIntervalSince1970, obtenga los componentes de fecha de eso usando el método NSCalendar's -componentsFromDate.

Referencia del SDK

Esto funciona para mí:

    float *lenghInSeconds = 2345.234513;
    NSDate *date = [NSDate dateWithTimeIntervalSinceReferenceDate:lenghInSeconds];
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];


    [formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];

    [formatter setDateFormat:@"HH:mm:ss"];
    NSLog(@"%@", [formatter stringFromDate:date]); 
    [formatter release];

La principal diferencia aquí es que necesita ajustar la zona horaria.

O está mi método de clase. No maneja años, pero eso podría agregarse fácilmente, aunque es mejor para pequeños intervalos de tiempo como días, horas y minutos. Toma en cuenta los plurales y solo muestra lo que se necesita:

+(NSString *)TimeRemainingUntilDate:(NSDate *)date {

    NSTimeInterval interval = [date timeIntervalSinceNow];
    NSString * timeRemaining = nil;

    if (interval > 0) {

        div_t d = div(interval, 86400);
        int day = d.quot;
        div_t h = div(d.rem, 3600);
        int hour = h.quot;
        div_t m = div(h.rem, 60);
        int min = m.quot;

        NSString * nbday = nil;
        if(day > 1)
            nbday = @"days";
        else if(day == 1)
            nbday = @"day";
        else
            nbday = @"";
        NSString * nbhour = nil;
        if(hour > 1)
            nbhour = @"hours";
        else if (hour == 1)
            nbhour = @"hour";
        else
            nbhour = @"";
        NSString * nbmin = nil;
        if(min > 1)
            nbmin = @"mins";
        else
            nbmin = @"min";

        timeRemaining = [NSString stringWithFormat:@"%@%@ %@%@ %@%@",day ? [NSNumber numberWithInt:day] : @"",nbday,hour ? [NSNumber numberWithInt:hour] : @"",nbhour,min ? [NSNumber numberWithInt:min] : @"00",nbmin];
    }
    else
        timeRemaining = @"Over";

    return timeRemaining;
}

NSDate *date = [NSDate dateWithTimeIntervalSince1970:timeInterval];

// format: YYYY-MM-DD HH:MM:SS ±HHMM
NSString *dateStr = [date description];
NSRange range;

// year
range.location = 0;
range.length = 4;
NSString *yearStr = [dateStr substringWithRange:range];
int year = [yearStr intValue] - 1970;

// month
range.location = 5;
range.length = 2;
NSString *monthStr = [dateStr substringWithRange:range];
int month = [monthStr intValue];

// day, etc.
...

Aquí hay otra posibilidad, algo más limpia:

NSDate *date = [NSDate dateWithTimeIntervalSince1970:timeInterval];
NSString *dateStr = [date description];
const char *dateStrPtr = [dateStr UTF8String];

// format: YYYY-MM-DD HH:MM:SS ±HHMM
int year, month, day, hour, minutes, seconds;
sscanf(dateStrPtr, "%d-%d-%d %d:%d:%d", &year, &month, &day, &hour, &minutes, &seconds);
year -= 1970;

- (NSString *)convertTimeFromSeconds:(NSString *)seconds {

    // Return variable.
    NSString *result = @"";

    // Int variables for calculation.
    int secs = [seconds intValue];
    int tempHour    = 0;
    int tempMinute  = 0;
    int tempSecond  = 0;

    NSString *hour      = @"";
    NSString *minute    = @"";
    NSString *second    = @"";

    // Convert the seconds to hours, minutes and seconds.
    tempHour    = secs / 3600;
    tempMinute  = secs / 60 - tempHour * 60;
    tempSecond  = secs - (tempHour * 3600 + tempMinute * 60);

    hour    = [[NSNumber numberWithInt:tempHour] stringValue];
    minute  = [[NSNumber numberWithInt:tempMinute] stringValue];
    second  = [[NSNumber numberWithInt:tempSecond] stringValue];

    // Make time look like 00:00:00 and not 0:0:0
    if (tempHour < 10) {
        hour = [@"0" stringByAppendingString:hour];
    } 

    if (tempMinute < 10) {
        minute = [@"0" stringByAppendingString:minute];
    }

    if (tempSecond < 10) {
        second = [@"0" stringByAppendingString:second];
    }

    if (tempHour == 0) {

        NSLog(@"Result of Time Conversion: %@:%@", minute, second);
        result = [NSString stringWithFormat:@"%@:%@", minute, second];

    } else {

        NSLog(@"Result of Time Conversion: %@:%@:%@", hour, minute, second); 
        result = [NSString stringWithFormat:@"%@:%@:%@",hour, minute, second];

    }

    return result;

}