You can link one master calendar only to one date field. You have two. So perhaps you want two calendars. Otherwise you may need to remodel your data so that you have only one date field, optionally with a field that specifies which kind of date the record stores. You could for example create records for each day a patient was submitted between the admission and discharge dates. How to do that is explained in this blog post: Creating Reference Dates for Intervals
For more information about using multiple versus single master calendars see these pages and the comments on those pages: