With the year 1873, the Gregorian calendar was introduced to Japan. While the Christian way of numbering years is commonly used in Japan today, a parallel numbering system for years based on the reigns of emperors is also frequently applied. The year 2000, for example, which happened to be the 12th year of the reign of the current emperor, whose posthumous name will be Heisei, is called "Heisei 12".
Before the Gregorian calendar, lunar calendars, which were originally imported from China, were used in Japan for many centuries. The lunar calendars were based on the cycle of the moon, resulting in years of twelve months of 29 or 30 days (the moon takes about 29 1/2 days to circle the earth), and an occasional 13th month to even out the discrepancy to the solar cycle of 365 1/4 days, i.e. the discrepancy to the seasons. Various features of the lunar calendar remain intact in today's Japan. For example, years are still commonly associated with the twelve animals: mouse, cow, tiger, rabbit, dragon, snake, horse, sheep, monkey, rooster, dog and pig.

Click on the picture to enlarge the Japanese style calendars. More pictures will be uploaded soon.