This is the twenty-one day period following Śākyamuni’s enlightenment, during which he verified his awakening. Beneath the Bodhi Tree, the Buddha manifested as Vairocana and taught the Flower Garland Sūtra to the Bodhisattvas of the Dharma-body who had practiced sufficiently in their previous lives. Although Universal Worthy Bodhisattva and Mañjuśrī Bodhisattva understood his teaching, those with inferior capacities did not.
2. THE SECOND PERIOD: THE DEER PARK TEACHINGS
After he became certain of his awakening, Śākyamuni left the Bodhi tree and went to Deer Park in modern day Benares. There he taught the Hinayāna teaching to five monks, or bhikṣu, including Ājñāta-Kauṇḍinya. Over the next twelve years, he taught the Agama sūtras to the people according to their capacities: the four noble truths to the śrāvakas, the twelve-fold chain of dependent origination to the pratyekabuddhas, and the six perfections to the bodhisattvas. Although he taught at locations other than Deer Park, this period is called the Deer Park period, as that is where he first began preaching the Agama sūtras.
3. THE THIRD PERIOD: THE EXPANDED TEACHINGS
The Period of Expanded Teaching lasted eight years. In Sino-Japanese this period is called “Hōdō.” Hō, means wide, and in this period the teachings of both Mahāyāna and Hinayāna were taught, so the teachings were widened or expanded. Dō, or tō, means equal. The teachings of Hinayāna and Mahāyāna were taught to people equally, according to their capacities. Only the Mahāyāna teaching was taught during the first period and only the Hinayāna teaching during the second period, but this third period links Hinayāna and Mahāyāna, so this teaching is also called the “common” teaching. By comparing Hinayāna and Mahāyāna, people found the Mahāyāna teaching within the Hinayāna teaching, and people therefore learned Mahāyāna Buddhism. Sūtras expounded in this period included the Vimalakīrti Sūtra, Questions of Brahma Excellent Thought Sūtra, Entering Laṇkā Sūtra, Supreme Golden Light Sūtra, and the Lion’s Roar of Queen Śrimālā Sūtra.
4. THE FOURTH PERIOD: THE WISDOM TEACHINGS
This period lasted twenty-two years. Here Śākyamuni expounded the Perfection of Wisdom and its doctrines. According to the Perfection of Wisdom teaching, there is no way to awakening other than Mahāyāna teaching, which is based on the concept of emptiness.
5. THE FIFTH PERIOD: THE LOTUS AND NIRVANA SUTRAS
This period comprises the last eight years of Śākyamuni’s teaching. He taught the Lotus Sūtra for eight years, followed by the Nirvāṇa Sūtra. There are varying ideas of how long the Nirvāṇa Sūtra was preached. According to the Preaching Travels Sūtra and the Hinayāna Nirvāṇa Sūtra it was three months just before Śākyamuni’s passing. Based on the contents of the Mahāyāna Nirvāṇa Sūtra it was one day and one night.
