Like many countries, Japan uses a 12-month calendar. The names are very simple. January is literally “Month one” 一月, February is “Month two” 二月, etc.

However, before the Meiji Restoration (mid-1800s) it was common to use an older 12-month system. These months’ names referenced the weather and the seasons.

December is 師走.

The kanji:

師 = teacher or religious mentor. In this case it means “monk”.

走 = running

December is known as “師走 – Shiwasu” in Japanese. The word “師” refers to teachers, mentors, or those who serve as role models—leaders in Buddhism and Christianity, for instance. The word “走” means “to run.”

Why is December called Shiwasu? It is commonly said that even those who are usually calm and composed, like monks, are so busy in December that they seem to be running around.

One reason monks are particularly busy at the year’s end is the annual Buddhist ritual called Butsumyō-e, held in late December. This ceremony involves chanting the names of Buddhas and Bodhisattvas, repenting for the sins committed during the year and praying for spiritual and physical purification.

While ordinary individuals can also participate in this ritual, for those who cannot, monks travel to various temples to perform it on their behalf.

In addition to such ceremonies, many families honor their ancestors during the New Year period, which adds to the concentrated activity. This custom seems to have become the more prominent reason for the busyness of the year-end season in modern times.

炬燵（こたつ Kotatsu) :

Even today in Japan, many households bring out their kotatsu to keep warm. A kotatsu is a heating device consisting of a frame (known as kotatsu-yagura or kotatsu-desk) placed on the floor or tatami mats, with a heat source inside and covered with a blanket to create a cozy, localised warm space.

The history of the kotatsu dates back approximately 600 years to the Muromachi period. At that time, Japanese people used built-in hearths called irori to stay warm. It is said that the kotatsu originated when people placed clothing over these hearths to warm their feet.