You may have heard on the news that "Today is Tanabata, July 7th!", but in Hokkaido, Tanabata is generally celebrated on August 7th. If you are a Hokkaido resident, you may have wondered, "Why is it different only in Hokkaido?"

In fact, while Tanabata is celebrated in July in some areas of Hokkaido, such as Hakodate and Nemuro, the Sendai Tanabata Festival in Tohoku is held in August, so the dates for Tanabata vary depending on the region. What is the reason for this difference?

First of all, why is Tanabata celebrated on July 7th?

Tanabata is a star festival that was introduced to Japan from China long ago. It began from the legend that the two stars, Orihime and Hikoboshi, who face each other across the Milky Way, can only meet on July 7th.

On summer nights, you can see the "Great Summer Triangle" in the eastern sky, consisting of three stars: Vega, Altair, and Deneb. Two of the stars that make up the triangle, Vega, a first magnitude star in the constellation Lyra, is known as "Orihime" or "Vega Star," and Altair, a first magnitude star in the constellation Aquila, is known as "Hikoboshi" or "Kengyusei." It is said that this legend was born because these stars look especially beautiful on July 7th.

The reason for the different dates is the difference between the "old calendar" and the "new calendar."

Tanabata was originally celebrated on July 7th, but many areas in Hokkaido celebrate it in August due to the difference between the old and new calendars. On November 9th, 1872 (Meiji 5), the Meiji government decided to abolish the old lunisolar calendar that had been used until then, and to adopt the Gregorian calendar (solar calendar) as the new calendar from January 1st of the following year. As a result, December 3rd, Meiji 5, became January 1st, Meiji 6, effectively moving it up by about a month.

In areas where Tanabata falls on July 7th, they kept the original date of July 7th in the lunar calendar even after switching to the Gregorian calendar, and celebrated Tanabata on July 7th in the Gregorian calendar. On the other hand, in areas where Tanabata falls on August 7th, they only kept the original date of the 7th, and celebrated Tanabata a month later on August 7th, because July 7th in the lunar calendar is roughly early August in the Gregorian calendar.

Incidentally, the reason why Obon is celebrated in some areas in July and others in August is due to the difference between the old and new calendars, just like Tanabata. In Hakodate and Nemuro, both Tanabata and Obon are celebrated in July.