.计算时间间隔多少秒,可以使用到计算程序代码执行时间

方式1:

CFTimeInterval begin = CFAbsoluteTimeGetCurrent();    for (NSInteger i = 0; i< 5000; i++) {        NSLog(@"123456");    }    CFTimeInterval end = CFAbsoluteTimeGetCurrent();

方式2:

NSDate *begin = [NSDate date];    for (NSInteger i = 0; i< 5000; i++) {        NSLog(@"123456");    }    NSDate *end = [NSDate date];        NSLog(@"%f",[end timeIntervalSinceDate:begin]);

方式3:

NSTimeInterval start = [[NSDate date] timeIntervalSince1970]*1;    for (NSInteger i = 0; i< 5000; i++) {        NSLog(@"------%ld",i);    }    NSTimeInterval end = [[NSDate date] timeIntervalSince1970]*1;    NSTimeInterval value = end - start;    int second = (int)value %60;//秒    int minute = (int)value /60%60;    int house = (int)value / (24 * 3600)%3600;    int day = (int)value / (24 * 3600);    NSString *str;    if (day != 0) {        str = [NSString stringWithFormat:@"耗时%d天%d小时%d分%d秒",day,house,minute,second];    }else if (day==0 && house != 0) {        str = [NSString stringWithFormat:@"耗时%d小时%d分%d秒",house,minute,second];    }else if (day== 0 && house== 0 && minute!=0) {        str = [NSString stringWithFormat:@"耗时%d分%d秒",minute,second];    }else{        str = [NSString stringWithFormat:@"耗时%d秒",second];    }    return str;

 

计算N天前日期

/** 获取指定天数前的日期 @param beforeDay 多少天之前 */- (NSString *)getDateBeforeDay:(NSInteger)beforeDay{    NSDateFormatter *dateFormat = [[NSDateFormatter alloc]init ] ;    [dateFormat setDateFormat:@"yyyy-MM-dd"] ;        NSString *localDateStr = @"";    BOOL isSystem = YES;//[ZTEConfigrationList currAppTimeZone]; 是否是系统时区    if (!isSystem) {        //获取本地时间        [dateFormat setTimeZone:[NSTimeZone timeZoneWithName:@"Asia/Hong_Kong"]];        localDateStr = [dateFormat stringFromDate:[NSDate date]];    } else {        localDateStr = [dateFormat stringFromDate:[NSDate date]] ;    }        NSDate *date = [dateFormat dateFromString:localDateStr];        //计算day天以前时间    NSDate *someDaysAgoDate = [NSDate dateWithTimeInterval:-(beforeDay-1) * 24 * 60 * 60 sinceDate:date];    return [dateFormat stringFromDate:someDaysAgoDate];}

当前2017-09-16 运行结果: 2017-09-18