anyway to limit hotspot user just can use for 30days?

mean start from 1st Jan until 31 Jan...

1st of feb, user cannot access again...

You could easily do this with something like Radius Manager.

http://www.dmasoftlab.com/cont/home

You could easily do this with something like Radius Manager.

http://www.dmasoftlab.com/cont/home

but i am giving free service to my clients..

If the cost of radius manager is a concern use Mikrotik's User Manager.

http://wiki.mikrotik.com/wiki/Manual:User_Manager

If the cost of radius manager is a concern use Mikrotik's User Manager.

http://wiki.mikrotik.com/wiki/Manual:User_Manager

may i know where to download user manager?
why i did't see any link to download at http://www.mikrotik.com/download ?

It's there. It is in the .zip file of the appropriate package for your router. You drag the user-manager.npk over to your router and reboot to install.