Tenchi Meisatsu

A member of the Yasui House in 1661, Yasui Santetsu also lives under the name Shibukawa Harumi, exploring mathematics and astronomy. Harumi dedicates himself to developing a new Japanese calendar. At the time, Japan used an outdated Chinese lunar-solar calendar that had fallen behind by two days in marking the winter solstice. Using his own astronomical observations, he worked to reform it. The story is based on the real-life astronomer and calendar reformer Shibukawa Harumi, who lived from 1639 to 1715.