Mysql from_unixtime来自两个不同时间戳的相同日期时间

I am having a weird problem with mysql. I am using FROM_UNIXTIMESTAMP to convert timestamp to datetime. The problem is two different timestamp is resulting into same datetime. How can it be possible?

Here what I got from mysql-

SELECT from_unixtime( '1456017720' ) , from_unixtime( '1456021320' )

Output-

2016-02-20 23:22:00 2016-02-20 23:22:00

enter image description here

This is the result of SHOW VARIABLES LIKE "%version%";

innodb_version 5.6.26-76.0 
protocol_version 10 
slave_type_conversions version 10.0.23-MariaDB 
version_comment MariaDB Server 
version_compile_machine x86_64 
version_compile_os Linux 
version_malloc_library bundled jemalloc