The lack of a perceived need for precision as well as isolationist practices in Japan often kept calendar reforms adopted in China and elsewhere in the world from finding their way here. While a lunar calendar was "officially" established in Japan in 692 by the Emperor "Jitou", accurate methods of astronomical observation and calculation found little acceptance. A good example of the difficulty of Japanese "astronomers" may be seen in the calendar reform of 1684. For the first time, Japan got a lunar calendar based on Japanese longitudinal coordinates. This reform was the work primarily of the "calendar scholars" Harumi Shibukawa and Anbu Yasutomi with their student and later colleague, Jinzan Tani.
In many ways, theirs is a sad story. Shibukawa and Yasutomi seem to have been more theoretical while Tani held sway in empirical investigation and calculation. Seeing the current calendar to be in error by up to two days, they had an uphill struggle against a general obsession with astrology, mystic assumptions of the emperor, disinterest by the Shogunate, and their own lack of information from the "outside" world. By this time, Jesuit missionaries, well aware of events in Europe, were helping Chinese calendar scholars to develop accurate ephemerides and thus more accurate calendars. Unaware of these developments, yet seeing "consistent" inconsistencies in their own observations and calculations, the three scholars of Japan, especially the empirically oriented Tani, worked hard to develop an accurate means of reckoning. While they were able to get a more accurate version of an older (1282) calendar from China adopted, they were nevertheless restricted by time and place from making advances that would have truly made their observations meaningful. While other reforms were introduced in the later Edo era, it was not until the Meiji Restoration that Japan joined the world stage in having a consistent and relatively accurate method for recording dates. This, of course, was the Gregorian calendar.
In modern times, many of the aspects of the "old" lunar system remain in Japanese culture including determination of some festivals and observances (such as "Tanabata" on the seventh day of the seventh month), names for years after the current Emperor (1996 is Heisei 8), and the old Chinese sexagesimal and astrological associations (familiar animals such as mouse, cow, cat, rabbit, etc.). While many Japanese faithfully continue to plan events with their "supplemental" lunar calendars, the Gregorian system is officially recognized for all legal transactions.