NSDate

======================== ios 如何获得系统时间和日期===================

1. 获得系统时间

1   　　　 NSDate *senddate=[NSDate date];2         NSDateFormatter *dateformatter=[[[NSDateFormatter alloc] init] autorelease];3         [dateformatter setDateFormat:@"YYYY-MM-dd-HH-mm-ss-a"];4         NSString *locationString =[dateformatter stringFromDate: senddate];5         NSLog(@"当前时间=%@",locationString);

 

2.获得当前时间【好像是以0时区为标准】

　　　　 NSDate *myDate = [NSDate date];        NSLog(@"myDate = %@",myDate);

 

3.获得系统日期

　　　 NSCalendar *cal = [NSCalendar currentCalendar];        NSUInteger unitFlags = NSDayCalendarUnit|NSMonthCalendarUnit|NSYearCalendarUnit;        NSDateComponents * conponent = [cal components:unitFlags fromDate:senddate];        NSInteger year = [conponent year];        NSInteger month = [conponent month];        NSInteger day = [conponent day];        NSString *dateString = [NSString stringWithFormat:@"%4d年%2d月%2d日",(int)year,(int)month,(int)day];        NSLog(@"当前日期 = %@",dateString);

 

4.从字符串来获得NSDate

1  　　    NSString *strYear = @"1988"; 2         NSString *strMonth = @"09"; 3         NSString *strDay = @"18"; 4         NSString *strHour = @"5"; 5         NSString *strMinutes = @"18"; 6         NSString *strSec = @"20"; 7          8         NSString *morelocationString = [NSString stringWithFormat:@"%@-%@-%@ %@:%@:%@" 9                                         ,strYear,strMonth,strDay,strHour,strMinutes,strSec];10         11         //根据时间字符串获得NSDate12         NSDateFormatter *formatter = [[[NSDateFormatter alloc] init] autorelease];13         [formatter setDateFormat:@"YYYY-MM-dd HH:mm:ss"]; // 这个格式必须跟33行一致14         NSDate *oldDate = [formatter dateFromString:morelocationString];15         NSLog(@"oldDate = %@",[dateformatter stringFromDate:oldDate]);

 

5. 第二天的当前时间

1         NSTimeInterval secondsPerDay = 24*60*60;2         NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:secondsPerDay];3         NSLog(@"myDate = %@",tomorrow);

 

6.前一天的当前时间

　　　　 NSTimeInterval secondsPerDay1 = 24*60*60;        NSDate *now = [NSDate date];        NSDate *yesterDay = [now addTimeInterval:-secondsPerDay1];        NSLog(@"yesterDay = %@",yesterDay);