July 7 is Tanabata in Japan, not a national holiday but a well known one at the least.
Tanabata has its origins in the meeting of the stars Vega and Altair, known in Japanese as Orihime and Hikoboshi, respectively.
The abovelinked Wikipedia page has a lot of information on methods of celebrating Tanabata, but typically when you think of Tanabata you think of tanzaku, which are small strips of paper on which you write wishes. The tanzaku are typically then tied to bamboo branches that are mounted in a base of some sort. At the beginning of my Tuesday morning Japanese class at the Okayama International Center we made tanzaku, which was a first for me.
Technically the wishes are to the stars or the spirits that inhabit the stars or something like that. (Remember traditional Japanese religion is animistic, so there are no rules as to what can and can’t be a god or a spirit.) Knowing this it was a little weird to make tanzaku on Tuesday, but instead of refusing to participate I decided that my wishes would be directed to God and not to the stars (which, let’s face it, can’t do anything in the first place). For many Japanese I would imagine that not much significance is placed on the tanzaku—it’s just something that they do, rather than really trust or believe in.