According to legend, the stars Vega and Altair are really the lovers Orihime and Hikoboshi. Long ago they were separated by the god of the sky Tentei (天帝). They're only permitted to reunite once a year on July 7th (or August 7th depending on region).
Tanabata is celebrated by hanging long colorful strips of paper outside from bamboo branches (sasa). People write their wishes on the paper. It's thought that the same celestial forces that reunite Orihime and Hikoboshi can also grant wishes.
Each year there are dozens of Tanabata festivals throughout Japan including the massive Sendai Tanabata Festival. Tanabata is also celebrated by Japanese communities outside Japan (e.g. as part of Nisei Week in Los Angeles).
The StoryOrihime (織姫 ~ the Weaving Princess) was the daughter of the god Tentei (King of the Sky). Each day she wove beautiful garments for Tentei while sitting on the banks of the Milky Way. She was very beautiful but had no time to meet a romantic partner (too busy weaving).
Tentei took pity on her and introduced her to a single guy — Hikoboshi (彦星 ~ the Cow Herder Star). Tentei's plan worked all too well. Orihime and Hikoboshi instantly fell in love and married. They were so deeply in love that Orihime forgot about weaving and Hikoboshi let his cows stray.
Tentei was enraged when he found that Orihime's weaving had stopped. He separated the lovers across the expanse of the Milky Way. Only after his daughters tears and pleading did he agree to let them meet once a year on the 7th day of the 7th month.
Tanabata CelebrationsJapanese shopping districts put up decorations for Tanabata. It's common for families with young children to do the same at home.
Japan's many Tanabata festivals often include dancing, competitions, parades and festival foods.
As with most summer festivals, people dress in yukata for Tanabata.
Tanabata's romantic story means that the festival is popular with couples. It's also a time for star gazing — to try to spot the reunited lovers.
Tanabata has spread around the World with Japanese immigration. There's a large Tanabata festival in Sao Paulo, Brazil on the first weekend of July.