1. 獲取當(dāng)天星期,月份颓芭，年份

    NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
    NSDate *now = [NSDate date];
    NSDateComponents *componets = [[NSDateComponents alloc] init];
    NSInteger unitFlags = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitWeekday ;
    componets = [calendar components:unitFlags fromDate:now];

    NSInteger weekday = [componets weekday];

2. 將NSDate 轉(zhuǎn)換為 NSString

// 將NSDate 中的數(shù)據(jù)提取出來彻犁，組成字符串
// 第一步：日期對(duì)象
NSDate * nowDate = [NSDate date];
// 第二步：創(chuàng)建NSDateFormatter對(duì)象
NSDateFormatter * formatter = [[NSDateFormatter alloc]init];
// 第三步：設(shè)定日期轉(zhuǎn)換的格式(提起數(shù)據(jù)的方式)
[formatter setDateFormat:@"yyyy/MM/dd"];  //yyyy 年 MM 月 dd 日
// eeee星期  MMMM大寫月份  QQQQ季度  zzzz時(shí)區(qū)  hh:mm:ss 時(shí)：分：秒
[formatter setDateFormat:@"yyyy-MM-dd hh:mm:ss eeee MMMM QQQQ zzzz" ];
// 第四步：轉(zhuǎn)換
NSString * timeStr = [formatter stringFromDate:nowDate];
NSLog(@"%@",timeStr);

3. 將NSString轉(zhuǎn)換為NSDate：將NSString中包含的與日期有關(guān)的信息提取出來，創(chuàng)建NSDate對(duì)象

// 第一步：包含信息的字符串
NSString * timeStr = @"2014年05月01日 10點(diǎn)23分18秒";

// 第二步：創(chuàng)建NSDateFormatter對(duì)象
NSDateFormatter * formatter = [[NSDateFormatter alloc]init];

// 第三步：設(shè)置日期轉(zhuǎn)換格式(必須匹配)
[formatter setDateFormat:@"yyyy年MM月dd日 HH點(diǎn)mm分ss秒"];
//[formatter setDateFormat:@"yyyy年MM月dd日 hh點(diǎn)mm分ss秒"];

// 第四步：轉(zhuǎn)換
// NSDate * date = [formatter dateFromString:timeStr];
NSDate * date = [formatter dateFromString:timeStr];
NSLog(@"%@", date);

4. -------------計(jì)算時(shí)間間隔 在新聞時(shí)候應(yīng)該可以用到--------------

NSDate * newTime = [NSDate date];
NSString * timeStr = @"2015-12-12 00:30:20";
NSDateFormatter * formater = [[NSDateFormatter alloc]init];
[formater setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate * date = [formater dateFromString:timeStr];
NSTimeInterval inter = [newTime timeIntervalSinceDate:date];
if (inter < 60 ) {
     NSLog(@"剛剛");
} else if (inter < 3600 && inter > 60){
     inter /= 60;
     NSLog(@"%f分鐘前",inter);
} else if (inter > 3600 ){
     inter /= 3600;
     NSLog(@"%f小時(shí)前",inter);
}

5. 獲取當(dāng)前的時(shí)間

    // 下面的第一個(gè)方法不提倡
//     NSDate *now1 = [[NSDate alloc]initWithTimeIntervalSinceNow:8*60*60];
//    NSLog(@"now %@",now1);
//

    NSDate * today = [NSDate date];
    NSTimeZone *zone = [NSTimeZone systemTimeZone];
    NSInteger interval = [zone secondsFromGMTForDate:today];

    NSDate *localeDate = [today dateByAddingTimeInterval:interval];
    // 時(shí)間轉(zhuǎn)換成時(shí)間戳
    NSString *timeSp = [NSString stringWithFormat:@"%ld",(long)[localeDate timeIntervalSince1970]];
    NSLog(@"timeSp : %@", timeSp);

6. 時(shí)間戳轉(zhuǎn)換成時(shí)間類型（NSDate） 這個(gè)很久寫的斑响，有點(diǎn)亂菱属，自己看吧
   時(shí)間戳轉(zhuǎn)換成日期

    NSDate *currentTime = [NSDate dateWithTimeIntervalSince1970:[timeSp intValue]];
    NSLog(@"currentTime %@",currentTime);

    NSDateFormatter *dateformatter=[[NSDateFormatter alloc] init];
    [dateformatter setDateFormat:@"yyyy-MM-dd HH:MM:ss"];
    NSString * locationString=[dateformatter stringFromDate:currentTime];
     NSLog(@"LocationString %@",locationString);

//    -------------------------
    NSDate *currentTime2 = [NSDate date];
    NSLog(@"currentTime2 %@",currentTime2);
    NSString *timeSp2 = [NSString stringWithFormat:@"%ld",(long)[currentTime2 timeIntervalSince1970]];
    NSDate * current = [NSDate dateWithTimeIntervalSince1970:[timeSp2 intValue]];
    NSDateFormatter *dateformatter2=[[NSDateFormatter alloc] init];
    [dateformatter2 setDateFormat:@"yyyy-MM-dd HH:MM:ss"];
    NSString * locationString2 =[dateformatter2 stringFromDate:current];
     NSLog(@"LocationString2 %@",locationString2);