NSDate 时间比较...等

http://blog.csdn.net/reylen/article/details/8560128


创建当前时间
NSDate *date = [NSDate date];  

从现在开始的24小时
        NSTimeInterval a_day = 24*60*60;
        NSDate *tomorrow = [NSDate dateWithTimeIntervalSinceNow:a_day];
根据已有日期创建日期
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NSTimeInterval a_day = 24*60*60;  
NSDate *date = [NSDate date];  
NSDate *tomorrow = [date addTimeInterval: date];  
日期比较
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      BOOL isEqual = [date isEqualToDate:tomorrow];  
f(isEqual){  
NSLog(@"equal");  

//获取较早的日期
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NSDate *earlier_date = [tomorrow earlierDate:date];  
  NSLog(@"earlierDate  = %@",earlierDate);  

//较晚的日期
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NSDate *laterDate = [tomorrow laterDate:date];  
NSLog(@"laterDate  = %@",laterDate);  

//两个日期之间相隔多少秒
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NSTimeInterval secondsInterval= [date timeIntervalSinceDate:tomorrow];  
NSLog(@"secondsInterval=  %lf",secondsInterval); 
 
 //通过NSCalendar类来创建日期
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NSDateComponents *comps = [[NSDateComponentsalloc]init];  
[comps setMonth:01];  
[comps setDay:31];  
[comps setYear:2013];  
NSCalendar *calendar = [[NSCalendaralloc]initWithCalendarIdentifier:NSGregorianCalendar];  
NSDate *date = [calendar dateFromComponents:comps]; 
 
 //从已有日期获取日期
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unsigned units  = NSMonthCalendarUnit|NSDayCalendarUnit|NSYearCalendarUnit;  
NSDateComponents *_comps = [calendar components:units fromDate:date];  
NSInteger month = [_comps month];  
NSInteger year = [_comps year];  
NSInteger day = [_comps 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 *dateString = [formatter stringFromDate:date];  
NSLog(@"dateString = %@",dateString);  
NSLog(@"formater = %@",formatter);  

//获取日期格式对象
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- (NSDateFormatter *)getDateFormatter {  
    if (dateFormatter == nil) {  
    dateFormatter = [[NSDateFormatter alloc] init];  
    [dateFormatter setDateStyle:NSDateFormatterMediumStyle];  
    [dateFormatter setTimeStyle:NSDateFormatterNoStyle];  
    }  
    return dateFormatter;  
}  

时间比较

-(int)compareDate:(NSString*)date01 withDate:(NSString*)date02{
    int ci;
    NSDateFormatter *df = [[NSDateFormatter alloc] init];
    [df setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSDate *dt1 = [[NSDate alloc] init];
    NSDate *dt2 = [[NSDate alloc] init];
    dt1 = [df dateFromString:date01];
    dt2 = [df dateFromString:date02];
    NSComparisonResult result = [dt1 compare:dt2];
    switch (result)
    {
        //date02比date01大
        case NSOrderedAscending: ci=1; break;
        //date02比date01小
        case NSOrderedDescending: ci=-1; break;
        //date02=date01
        case NSOrderedSame: ci=0; break;
        default: NSLog(@"erorr dates %@, %@", dt2, dt1); break;
    }
    return ci;
}