It's not about the artwork - though this year the calendar features the first twelve of "The Seventy Maxims of Maximally Effective Mercenaries" from Howard Tayler's Schlock Mercenary comic, rather than pictures of horses as has been the case the last several years.
This is about the numbers. Or the size and color of them. This calendar reminds me one from a few years ago. Both have small numbers for the dates. That's great if you're up close and need space to write lots of stuff for that date. It's not so great from a distance where you simply want to see the numeric date.
The next year, after the tiny type a while back, I found a calendar I liked with nice big date numbers. But they were various, muted, nearly (if not) pastel colors which also made them harder to read from a distance. And the colors were random. It wasn't "Holidays are red" or "Mondays are blue, Tuesdays are orange,..." Thus no useful information was added but the decoration made the thing less useful than it should have been.
It strikes me as odd that these problems exist. A calendar isn't a new or terrible complex thing. They've been around for a long, long time. One would expect readability from common uses (halfway across a small room doesn't seem to be asking too much) would be one of those well and truly solved problems. Evidently it is not.
 Computing some dates, such as Easter, can be complicated, however.