It was 9 full months after the Buddha got the Enlightenment, on the full moon day of 6th lunar month, 45 years before the Buddhist era. On the full moon day of the 3rd lunar month, Makha, of the year, 4 special events happened:
1. There were 1,250 Sangha followers, that came to see the Buddha that evening without any schedule.
2. All of them were "Arhantas', the Enlightened One, and all of them were ordained by the Buddha himself.
3. The Buddha gave those Arhantas the principles of the Buddhism, called "The Ovadhapatimokha". Those principles are: - To cease from all evil, - To do what is good, - To cleanse one's mind;
4. It was the full moon day.
Another important event, which happened on the same days (the full moon day of the 3rd lunar month) 44 years later, the last year of the Buddha's life, he decided to 'Parinibbhana', nirvana, leave the mind from the body or die. 3 months after that day (on the full moon day of the six lunar month -- we known as 'Visakha Bucha Day').