NSString *dateStr = @"1970-01-01 00:00:00 +0000";

    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];

    formatter.dateFormat = @"YYYY-MM-dd HH:mm:ss zzz";

    NSDate *date = [formatter dateFromString:dateStr];

备注:如果带时区的一定要加上 zzz