iOS 获取当前时间以及计算年龄（时间差）

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

第一种只得出年份差的年龄

    //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);

第二种得出具体到天的年龄

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];        //用来得到具体的时差    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

此项参考：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,这里可以设置成自己需要的格式
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,这里可以设置成自己需要的格式
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];