How do I set cron using performance page? I am not able to set up the performance setting for cron duration, and automatic cache clearing setting in admin performance page.

I am not able to find the exact issue. I am clearing the cache manually everyday currently.

Can anyone provide better solution for this?

I changed the settings, and clicked on the save button of the form,but settings are not saved. This happen with both cron and cache duration settings.
Please go to Cron Settings (http://example.com/drupal7/admin/config/system/cron) to set it, default is 3 hours.