Objiective-C中的NSDate

//得到当前的日期

     //       NSDate *date=[NSDate date];

     //NSLog (@"date:%@",date);

     //得到（24*60*60）即24小时之前的日期，dateWithTimeIntervalSinceNow;

     NSDate "yesterday = [NSDate dateWithTimeIntervalSinceNow: -(24 * 60 *60)]";

     NSLog(@"yesterday :%@",yesterday);

 

     NSDateFormatter  *formatter  =[[[NSDateFormatter  alloc] init]  autorelease];

     NSDate  *date =[NSDate  date];

     [formatter setTimeStyle:NSDateFormatterMediumStyle];

     NSCalendar *calendar = [[NSCalendaralloc] initWithCalendarIdentifier:NSGregorianCalendar]  autorelease];

     NSDateComponents  *comps  =  [[[NSDateComponentsalloc]  init]  autorelease];

     NSInteger   unitFlags  =  NSYearCalendarUnit  l

     NSMonthCalendarUnit  l

     NSDayCalendarUnit   l

     NSWeekdayCalendarUnit  l

     NSHourCalendarUnit    l

      NSMinuteCalendarUnit l

      NSSecondCalendarUnit;

      //int week=0;

     comps =  [calendar components:unitFlags  fromDate:date];

     int week  =  [comps  weekday];

     int year   =   [comps year];

      int month = [comps month];

      int day = [comps day];

      //[formatter  setDateStyle:NSDateFormatterMediumStyle];

     //This sets the lable with the updated  time.

     int hour =  [comps hour];

     int min  =  [comps minute];

      int sec = [comps  second];

      NSLog(@"week%d",week);

      NSLog(@"year%d",year);

      NSLog(@"month%d",month);

      NSLog(@"day%d",day);

      NSLog(@"hour%d",hour);

      NSLog(@"min%d",min);

      NSLog(@"sec%d",sec);

//得到毫秒

NSDateFormatter  *dateFormatter = [[NSDateFormatteralloc]  init];

[dateFormatter  setDateStyle:NSDateFormatterMediumStyle];

[dateFormatter setTimeStyle:NSDateFormatterShortStyle];

//[dateFormatter  setDateFormat:@"hh:mm:ss"]

[dateFormatter  setDateFormat:@"yyyy-MM-dd   HH:mm:ss.SSS"];

NSLog(@"Date@",[dateFormatter stringFormDate:[NSDate date]]);

[dateFormatter  release];