The original Tanabata date was based on the Japanese lunisolar calendar, which is about a month behind the Gregorian calendar. As a result, some festivals are held on July 7, some are held on a few days around August 7, while the others are still held on the seventh day of the seventh lunar month of the traditional Japanese lunisolar calendar, which is usually in August in the Gregorian Calendar.
The Gregorian date of "the seventh day of the seventh lunar month of the Japanese lunisolar calendar" for this year is 2011-08-06.
I guess we can pick the day we want.
