Hi Zeina.
Thanks for your question.
This article may help you learn how to create a custom Facebook Page Tab.
One way to do it that retains all your site’s styling is to iframe the HTTPS version of your site’s calendar.
If you need some coding help, you may want to ask your developer or reference our documentation and list of known customizers.
You may also want to request this as a new feature (or maybe search to see if the idea was already posted by someone else) at our plugins’ UserVoice page.
This allows others who are interested in that feature to easily voice their support. We frequently review suggestions there to find out which ones are popular, then we implement as many of them as we can.
If you post it / find it, feel free to link to it from here in case anyone comes across this forum thread in the future.