You might hear on the news, "July 7th is Tanabata!" but in Hokkaido, Tanabata is generally celebrated on August 7th. Residents of Hokkaido may have wondered, "Why is Hokkaido the only one that's different?"

In fact, while some areas in Hokkaido like Hakodate and Nemuro celebrate Tanabata on July 7th, the famous "Sendai Tanabata Festival" in the Tohoku region is held in August. The date of Tanabata varies by region. So, why did this difference come about?

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

Tanabata is a star festival that was introduced to Japan from ancient China. It originates from the legend of Orihime (the Weaver Princess) and Hikoboshi (the Cowherd), two lovers separated by the Milky Way who can only meet once a year on July 7th.

On a summer night, you can see the "Summer Triangle" in the eastern sky, formed by three stars: Vega, Altair, and Deneb. Two of the stars that make up this triangle are Orihime, the first-magnitude star Vega in the constellation Lyra, and Hikoboshi (also known as Kengyusei), the first-magnitude star Altair in the constellation Aquila. It is said that this legend was born because these stars appear particularly beautiful on July 7th.

The reason for the different dates lies in the difference between the "old calendar" and the "new calendar"

Tanabata was originally held on July 7th, but the reason many regions in Hokkaido celebrate it in August is due to the difference between the "old calendar" and the "new calendar." On November 9, 1872 (Meiji 5), the Meiji government decided to abolish the old lunisolar calendar and adopt the Gregorian (solar) calendar as the new standard, starting from January 1 of the following year. As a result, December 3, 1872, became January 1, 1873, effectively moving the calendar forward by about a month.

Regions that celebrate Tanabata on "July 7th" simply kept the original date of "July 7th" from the old calendar and applied it to the new calendar. On the other hand, regions that celebrate on "August 7th" do so because the old calendar's "July 7th" corresponds to early August in the new calendar. They kept the day, the "7th," but celebrate Tanabata a month later on "August 7th."

Incidentally, the Obon festival is also celebrated in either July or August depending on the region for the same reason—the difference between the old and new calendars. In Hakodate and Nemuro, both Tanabata and Obon are observed in July.