My daughter made this calendar in school, similar to this one. This is an example of kagami-mochi which I talked about in this old post. As Wikipedia explains, Kagami-mochi are broken apart after Oshogatsu (Japanese New Year, January 1st), and the mochi bricks inside are consumed on the second Saturday/Sunday of January.
Happy New Year!!
P.S. This post might be early for West Coast readers, but I didn’t want to miss readers in the EU and Asia. :p

かわいい作品ですね。まだ、年があけてませんが、Happy New Year.
来年もよろしくお願いします。。
ありがとう、ココミノさん!早すぎてごめんなさい。お客様に間に合ってように載せたのです。
じゃ、早いけど、明けましておめでとうございます。