Adding new field to Calendar Template Table

I am using the Calendar Template to build a new site. I would like to add a BirthDate, MemberDate, and GroupLetter(text) fields to the calender records. When I try to add any additional fields to the calcalendar table, the change resets the template's formatting of the monthly calendar view for the list page in the Page Designer. Is there a way I can add additional fields to the calcalendar table while retaining the original calender template for it's page? Thanks.