Though it refers to the night of July 7 (lunar calendar), Tanabata Matsuri is held in Japan either on July 7 or a month later on August 7 as Bon festival is also held either in July or in August, after the Meiji revision of the calendar.
7月7日(旧暦)の夜のことであるが、日本では明治改暦以降、お盆が7月か8月に分かれるように7月7日又は月遅れの8月7日に分かれて七夕祭りが行われる。