NSDate *date = [NSDate date];
NSLog(@"%@",date);//Thu Sep 13 16:16:13 2017
NSDate *date1 = [date dateByAddingTimeInterval:5];
NSLog(@"%@",date1);//Thu Sep 13 16:16:23 2017
//获取系统的
NSTimeZone *systemZone = [NSTimeZone systemTimeZone];
//获取本地的
NSTimeZone *localZone = [NSTimeZone localTimeZone];
NSInteger seconds = [systemZone secondsFromGMTForDate:date];
NSLog(@"%lu",seconds);//8小时
yyyy 年 MM 月 dd 日 HH 24小时 hh 12 小时 mm 分钟 ss 秒 Z 时区
NSDate *now = [NSDate date];
NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss z";
NSString *dateStr = [formatter stringFromDate:now];
NSLog(@"%@",dateStr);//2018-09-13 17:17:33 GMT+8
NSString *dateString = @"2018-09-13 17:17:33 GMT+8";
NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss Z";
NSDate *lastdDate = [formatter dateFromString:dateString];