iOS 计算时间差

- (NSString *)dateTimeDifferenceWithStartTime:(NSString *)startTime endTime:(NSString *)endTime{
    
    NSDateFormatter *date = [[NSDateFormatter alloc]init];
    [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSDate *startD =[date dateFromString:startTime];
    NSDate *endD = [date dateFromString:endTime];
    NSTimeInterval start = [startD timeIntervalSince1970]*1;
    NSTimeInterval end = [endD timeIntervalSince1970]*1;
    NSTimeInterval value = end - start;
    int minute = (int)value /60%60;
    int house = (int)value / (24 * 3600)%3600;
    int sum = house * 60 + minute + 1;
    NSString *str = [NSString stringWithFormat:@"%d",sum];
    return str;
}