1 // 当前时间创建NSDate

NSDate *myDate = [NSDate date];

NSLog(@"myDate = %@",myDate);

2 //从现在开始的24小时

NSTimeInterval secondsPerDay = 24*60*60;

NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:secondsPerDay];

NSLog(@"myDate = %@",tomorrow);

3//根据已有日期创建日期

NSTimeInterval secondsPerDay1 = 24*60*60;

NSDate *now = [NSDate date];

NSDate *yesterDay = [now addTimeInterval:-secondsPerDay1];

NSLog(@"yesterDay = %@",yesterDay);

4//比较日期

BOOL sameDate = [now isEqualToDate:yesterDay];

NSLog(@"sameDate = %lu",sameDate);

4.1//获取较早的日期

NSDate *earlierDate = [yesterDay earlierDate:now];

NSLog(@"earlierDate  = %@",earlierDate);

4.2//较晚的日期

NSDate *laterDate = [yesterDay laterDate:now];

NSLog(@"laterDate  = %@",laterDate);

//两个日期之间相隔多少秒

NSTimeInterval secondsBetweenDates= [yesterDay timeIntervalSinceDate:now];

NSLog(@"secondsBetweenDates=  %lf",secondsBetweenDates);

//通过NSCALENDAR类来创建日期

NSDateComponents *comp = [[NSDateComponentsalloc]init];

[comp setMonth:06];

[comp setDay:01];

[comp setYear:2001];

NSCalendar *myCal = [[NSCalendaralloc]initWithCalendarIdentifier:NSGregorianCalendar];

NSDate *myDate1 = [myCal dateFromComponents:comp];

NSLog(@"myDate1 = %@",myDate1);

//从已有日期获取日期

unsigned units  = NSMonthCalendarUnit|NSDayCalendarUnit|NSYearCalendarUnit;

NSDateComponents *comp1 = [myCal components:units fromDate:now];

NSInteger month = [comp1 month];

NSInteger year = [comp1 year];

NSInteger day = [comp1 day];

//NSDateFormatter实现日期的输出

NSDateFormatter *formatter = [[NSDateFormatteralloc]init];

[formatter setDateStyle:NSDateFormatterFullStyle];//直接输出的话是机器码

//或者是手动设置样式[formatter setDateFormat:@"yyyy-mm-dd"];

NSString *string = [formatter stringFromDate:now];

NSLog(@"string = %@",string);

NSLog(@"formater = %@",formatter);

//获取日期格式对象

- (NSDateFormatter *)dateFormatter {

if (dateFormatter == nil) {

dateFormatter = [[NSDateFormatter alloc] init];

[dateFormatter setDateStyle:NSDateFormatterMediumStyle];

[dateFormatter setTimeStyle:NSDateFormatterNoStyle];

}

return dateFormatter;

}