This ordering site seems to be for Japan, but you can also purchase from overseas by using the following services.
However, the shipping costs are high. Besides, it's a calendar for Japan, so I don't think it's easy to use.
If you really want it, go ahead and buy it. It's also a good idea to buy one with a (offline/online) friends.
I plan to make postcards and a few acrylic art boards in the next month or two.
If you want them, or if you feel the shipping costs are too much, please wait for the right time.