Start with a decision, not decoration
A useful calendar brief names the reader, the decision or action the page should support, and the evidence required before design begins. For this project the audience is people tracking dates, events or campaigns across a month or year. The working objective is to make date relationships and scheduled information easy to scan without ambiguity. Write those two statements at the top of the brief and test every proposed section against them. Material that does not help the reader understand, trust or act should be removed, shortened or placed in a secondary channel.