Sharepoint 2013 calendar

Hi,

    I have two sites. site A and B. I want a common calendar that will be displayed in both sites and both the site members can add items to it. Changes made in the calendar from one site should be reflected on that calendar in another site. I created a calendar in site A and using calendar overlay created it in site B. But the problem i am facing is that when the calendar is edited in site B it is not getting reflected on site A. Please provide me some solutions.

Thanks in advance.

Regards,

Vignesh.