the business card of the BIG ones

A calendar is a system for connecting dates and days. Dates are generally based on the movement of astronomical objects. A calendar can also be a tool (usually on paper) used to describe this very system. Now, let's suppose that most of the human beings use one and the same system, a.k.a. the Gregorian calendar. Therefore, the difference in standards can be observed only in the calendar's theme, design and type - a working, a multi paper, a desk, or a pocket one.