It was the 8th day of the 12th lunar month, the story goes, that Siddhartha Gautama, also known as Shakyamuni, awoke from a week of meditation to view of the morning star - Venus - and exclaimed, "That's it! That's it! That's me! That's me that's shining so brilliantly!" In that single moment he fully realized the Dharma - that body of unalterable, immutable, unending Truth that he would spend the rest of his life teaching to others.
Zen Buddhists of Japanese traditions celebrate Bodhi Day (Rohatsu) on December 8th (even though "Rohatsu" means, literally, "the eighth day of the twelfth _lunar_month"); In China this important event is mostly forgotten in popular culture even though the day is not. The 8th day of the 12th lunar month, Laba Jie (làbajié), is celebrated yearly by billions as a reminder of the upcoming New Year. Knowledge of the Buddhist origins of the Laba festival has become lost to contemporary Chinese culture, just as the Christmas Tree has mostly forgotten origins that predate Christianity.
Many eastern Mahayana Buddhist traditions around the world now celebrate Wesak (in Sanskrit, Vaisakha - Buddha's birthday) to commemorate the Buddha's life and enlightenment on the first full moon of the fourth lunar month. Our Chinese Chan sect celebrates both the Buddha's Day of Enlightenment -- going by the lunar calendar (the 8th day of the 12th lunar month) -- as well as the Buddha's birthday (fatdáahn) on the 8th day of the 4th lunar month. Confusing? Regardless of the day we choose to celebrate Bodhi Day, commemorating the day of the Buddha's enlightenment offers a wonderful opportunity for us to reflect on our own spiritual practices and consider the significance of an event that changed the course of history for humankind some 2500 years ago.
http://www.hsuyun.org/chan/en/essays/es ... nment.html