NSDate处理

NSDateFormatter * dateFormatter = [[[NSDateFormatter alloc] init]autorelease];
    [dateFormatter setAMSymbol:@"AM"];
    [dateFormatter setPMSymbol:@"PM"];
    [dateFormatter setDateFormat:@"dd/MM/yyyy hh:mmaaa"];
    NSDate *date = [NSDate date];
    NSString * s = [dateFormatter stringFromDate:date];

// start by retrieving day, weekday, month and year components for yourDate
    NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDateComponents *todayComponents = [gregorian components:(NSDayCalendarUnit | NSMonthCalendarUnit | NSYearCalendarUnit) yourDate];
    NSInteger theDay = [todayComponents day];
    NSInteger theMonth = [todayComponents month];
    NSInteger theYear = [todayComponents year];

    // now build a NSDate object for yourDate using these components
    NSDateComponents *components = [[NSDateComponents alloc] init];
    [components setDay:theDay]; 
    [components setMonth:theMonth]; 
    [components setYear:theYear];
    NSDate *thisDate = [gregorian dateFromComponents:components];
    [components release];

    // now build a NSDate object for the next day
    NSDateComponents *offsetComponents = [[NSDateComponents alloc] init];
    [offsetComponents setDay:1];
    NSDate *nextDate = [gregorian dateByAddingComponents:offsetComponents toDate: yourDate options:0];
    [offsetComponents release];
    [gregorian release];

方法收集
/**
 该方法可扩展为获取n月之后 或 n月之前的NSDate对象
            获取n年之后 或 n年之前的NSDate对象
**/
 
//计算n天之后或者n天之前的NSDate
+ (NSDate *) getPriousDateFromDate:(NSDate *)date withDay:(int)day
{
    NSDateComponents *comps = [[NSDateComponents alloc] init];
    [comps setDay:day];
    NSCalendar *calender = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
    NSDate *mDate = [calender dateByAddingComponents:comps toDate:date options:0];
    [comps release];
    [calender release];
    return mDate;
}