Abhidhamma Day: According to Burmese tradition, this day celebrates when the Buddha went to the Tushita Heaven to teach his mother the Abhidhamma.
The BPS also publishes several books on the Abhidhamma, a systematic arrangement of the Buddha’s philosophical and psychological teachings, defining the theory that lies behind his more pragmatically oriented discourses: A Comprehensive Manual of Abhidhamma, a translation of the Abhidhammattha-sangaha complete with a detailed explanatory guide by the Burmese Sayadaw U Rewatadhamma and Bhikkhu Bodhi.
He compiled the Kathavatthu, in refutation of those views, and it was in this council that this text was approved and added to the Abhidhamma.