iOS NSDate与NSString相互转化

1.时间格式的字符串转date

 NSString *birthdayStr=@"1986-03-28 00:00:00.000";
 NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
 [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss.SSS"];
  [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:]];//解决8小时时间差问题
 NSDate *birthdayDate = [dateFormatter dateFromString:birthdayStr];

2.date转字符串

 NSDate *date = [NSDate date];
 NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
 [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
 NSString *strDate = [dateFormatter stringFromDate:date];