获取当前时间

        NSDate *now = [NSDate date];

        NSLog(@”now date is: %@”, now);

        NSCalendar *calendar = [NSCalendar currentCalendar];

        NSUInteger unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

        NSDateComponents *dateComponent = [calendar components:unitFlags fromDate:now];

        int year = [dateComponent year];

        int month = [dateComponent month];

        int day = [dateComponent day];

        int hour = [dateComponent hour];

        int minute = [dateComponent minute];

        int second = [dateComponent second];

        NSLog(@”year is: %d”, year);

        NSLog(@”month is: %d”, month);

        NSLog(@”day is: %d”, day);

        NSLog(@”hour is: %d”, hour);

        NSLog(@”minute is: %d”, minute);

        NSLog(@”second is: %d”, second);

计算年龄

第一种仅仅得出年份差的年龄

    //计算年龄

    NSString *birth = @"1993-10-30";

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];

    [dateFormatter setDateFormat:@"yyyy-MM-dd"];

    //生日

    NSDate *birthDay = [dateFormatter dateFromString:birth];

    //当前时间

    NSString *currentDateStr = [dateFormatter stringFromDate:[NSDate date]];

    NSDate *currentDate = [dateFormatter dateFromString:currentDateStr];

    NSLog(@"currentDate %@ birthDay %@",currentDateStr,birth);

    NSTimeInterval time=[currentDate timeIntervalSinceDate:birthDay];

    int age = ((int)time)/(3600*24*365);

    NSLog(@"year %d",age);

另外一种得出详细到天的年龄

NSCalendar *calendar = [NSCalendar currentCalendar];//定义一个NSCalendar对象

    NSDate *nowDate = [NSDate date];

    NSString *birth = @"1900-10-30";

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];

    [dateFormatter setDateFormat:@"yyyy-MM-dd"];

    //生日

    NSDate *birthDay = [dateFormatter dateFromString:birth];

    //用来得到详细的时差

    unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;

    NSDateComponents *date = [calendar components:unitFlags fromDate:birthDay toDate:nowDate options:0];

    if([date year] >0)

    {

        NSLog(@"%@",[NSString stringWithFormat:(@"%ld岁%ld月%ld天"),(long)[date year],(long)[date month],(long)[date day]]) ;

    }

    else if([date month] >0)

    {

        NSLog(@"%@",[NSString stringWithFormat:(@"%ld月%ld天"),(long)[date month],(long)[date day]]);

    }

    else if([date day]>0){

        NSLog(@"%@",[NSString stringWithFormat:(@"%ld天"),(long)[date day]]);

    }

    else {

       NSLog(@"0天");

    }

字符串、日期、Int转换

此项參考：http://blog.csdn.net/tt5267621/article/details/7720434

1、字符串转换为日期

NSDateFormatter* dateFormat = [[NSDateFormatter alloc] init];//实例化一个NSDateFormatter对象

[dateFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];//设定时间格式,这里能够设置成自己须要的格式

NSDate *date =[dateFormat dateFromString:@"1980-01-01 00:00:01"];

2、日期转换为字符串

NSDateFormatter* dateFormat = [[NSDateFormatter alloc] init];//实例化一个NSDateFormatter对象

[dateFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];//设定时间格式,这里能够设置成自己须要的格式

NSString *currentDateStr = [dateFormat stringFromDate:[NSDate date]];

3、字符串转int

Convert NSString to int

NSString *aNumberString = @"123";

int i = [aNumberString intValue];

4、int转字符串

Convert int to NSString

int aNumber = 123;

NSString *aString = [NSString stringWithFormat:@"%d", aNumber];