According to an ancient Chinese legend, on the seventh day of the seventh lunar month, two star-crossed lovers are able to traverse the sky and meet.
This date in Japan is called Tanabata, also know as the Star Festival, and these days is celebrated as a festive time to make wishes. The two lovers are Orihime, OH-REE-HE-MEH, (Vega) and Hikoboshi, HE-KO-BO-SHE, (Altair), and they are normally on opposite sides of the milky way, but on this one day they intersect.
There are many versions of the story, but there have a few things in common. Basically Orihime is the daughter of the Sky King and somehow she falls in love with Hikoboshi, a mere mortal. One or both of them then do something to piss her dad off and so in anger he separates them across the great river of Heaven and forbids them from ever meeting again. Orihime is so sad that her dad has a small change of heart and allows them to meet one day a year. Nice guy, eh?
Many places celebrate this event on July 7th, but a few hold to the old Japanese calendar (a lunar calendar) and so don’t celebrate it until August (the day changes every year, but always in August. Check wikipedia for more details than you could ever want). I have no idea when the actual intersection of Vega and Altair happens. Anyone know? Is it really on July 7th?
People generally celebrate this day by writing their wishes on small pieces of paper and hanging them on bamboo. The bamboo is sometimes set afloat on the a river or burned after the festival, tho this varies with each area.
Some pics from wikipedia:
