NSDateFormatter setDateFormat 自定义日期/时间格式

NSDateFormatter自定义日期/时间格式 ,简单的举一个例子，看下面的代码就可以了

NSDate *dateValue = [NSDate date];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"yyyy-MM-dd"];
dateValue = ((UIDatePicker *)sender).date;

self.teleplayDate.text = [dateFormatter stringFromDate:dateValue];//[NSString stringWithFormat:@"%@",dateValue];
self.wantToSaveTeleplayDate = self.teleplayDate.text;

下面附上几个格式：
yyyy:MM:dd G 'at' HH:mm:ss zzz 1996.07.10 AD at 15:08:56 PDT
EEE, MMM d, "yy Wed,july 10, '99
h:mm a 12:08 PM
hh 'o"clock' a,zzzz 12 o'clock PM, Pacific Daylight Time
K:mm a, z 0:00 PM, PST
yyyyy,MMMM.dd GGG hh:mm aaa 01996.july.10 AD 12:08 PM

下面是得到当前的年，月，日，时，分，秒。
NSCalendar *cal = [NSCalendar currentCalendar];
unsigned int unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit | NSSecondCalendarUnit;
NSDateComponents *dd = [cal components:unitFlags fromDate:date];
int y = [dd year];
int m = [dd month];
int d = [dd day];
int h = [dd hour];
int m = [dd minute];
int s = [dd second];