NSDate-常用操作及控制

对于NSDate常用操作整理，如有不足请补充

1，获取当前时区时间

//初始化时间段
NSDate *date = [NSDate date];
//获取当前时区
NSTimeZone *zone = [NSTimeZone systemTimeZone];
//以秒为单位返回当前应用程序与世界标准时间（格林威尼时间）的时差
NSInteger interval = [zone secondsFromGMTForDate: date];
//补充时差后为当前时间
NSDate *localeDate = [date  dateByAddingTimeInterval: interval];

2,将字符串格式化NSDate

NSString *dateStr=@"2013-08-13 20:28:40";
//格式化
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *fromdate=[dateFormatter dateFromString:dateStr];
//时区
NSTimeZone *fromzone = [NSTimeZone systemTimeZone];
//同例1
NSInteger frominterval = [fromzone secondsFromGMTForDate: fromdate];
NSDate *fromDate = [fromdate  dateByAddingTimeInterval: frominterval];
NSLog(@"fromdate=%@",fromDate);

//将NSDate转为NSString
NSString *strTime = [fromDate description];
//如果直接将NSDate格式化
NSDate  *recv = [NSDate dateFromString:recvTime withFormat:@"yyyy-MM-dd HH:mm:ss Z"];

3，比较两个时间相差（年月日，时分秒）

double intervalTime = [fromDate timeIntervalSinceReferenceDate] - [localeDate timeIntervalSinceReferenceDate];
 
long lTime = (long)intervalTime;
NSInteger iSeconds = lTime % 60;
NSInteger iMinutes = (lTime / 60) % 60;
NSInteger iHours = (lTime / 3600)$;
NSInteger iDays = lTime/60/60/24;
NSInteger iMonth = lTime/60/60/24/12;
NSInteger iYears = lTime/60/60/24/384;
 
NSLog(@"相差M年d月 或者 d日d时d分d秒", iYears,iMonth,iDays,iHours,iMinutes,iSeconds);

4，按日期排序

//与otherDate比较，相同返回YES
- (BOOL)isEqualToDate:(NSDate *)otherDate;
    
//与anotherDate比较，返回较早的那个日期 
- (NSDate *)earlierDate:(NSDate *)anotherDate;
    
//与anotherDate比较，返回较晚的那个日期
- (NSDate *)laterDate:(NSDate *)anotherDate;
  
//该方法用于排序时调用  
- (NSComparisonResult)compare:(NSDate *)other;

//. 当实例保存的日期值与anotherDate相同时返回NSOrderedSame
//. 当实例保存的日期值晚于anotherDate时返回NSOrderedDescending
//. 当实例保存的日期值早于anotherDate时返回NSOrderedAscending

5，从NSDate中获取年月日，时分秒

NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];   
  
NSInteger unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSWeekdayCalendarUnit |   

NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;   
       
NSDateComponents *comps  = [calendar components:unitFlags fromDate:date];   
       
int year = [comps year];   
int month = [comps month];   
int day = [comps day];   
int hour = [comps hour];   
int min = [comps minute];   
int sec = [comps second];

//获取数据有异常
//        NSError *error = [[NSError alloc] init];
//        NSData *pData = = [NSData dataWithContentsOfURL:URL options:NSDataReadingMapped error:&error];
//        NSLog(@"download string end error = %d", [error code]);
//        [error release];


判断12小时或24小时(制)

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setDateFormat:@"a"];
        NSString *AMPMtext = [dateFormatter stringFromDate:[NSDate date]];
        [dateFormatter release];
        if ([AMPMtext isEqualToString:@""]){
            NSLog(@"24小时制");
        }
        else {
            NSLog(@"12小时制");
        }