counting how many times a value/name appears on multiple worksheets

Hello,

I am a fairly basic Excel and I am trying to create a no brainer employee vacation tracker, I have 12 tabs for each month and a summary tab where I intend to enter all employees. On the summary tab I would like to have a formula in column I basically telling me how many times the empoloyee's name appears on the Calendar tabs. I attached an example. I have spent most of the day looking for answers...but frankly some of them went straight over my head. Any help or suggestions would be greatly appreciated.

Thanks,
Megan