The Five levels of Teaching After Buddha's Enlightenment 佛教的五時說教

From the time of his enlightenment until his death for forty-nine years, Shakyamuni Buddha taught at different levels according to the needs and capacities (abilities on understanding and practice) of different people. The Tiantai master Zhiyi (538-597) divided the Buddha's teachings to five periods by level:
佛陀由悟道開始直到離世的四十九年，根據不同人的需求與根機（理解與實踐的能力）而作出不同層次的說法。天台宗大師智顗（538-597）對佛陀的教法，按層次劃分為五個時期：

The level of "Avatamsaka": For revealed the essence of all phenomena in the universe and the supreme state of Buddha-wisdom to sentient beings who had transcended the world but had not yet attained Buddhahood, Shakyamuni Buddha expounding the Avatamsaka Sutra in his meditation state on the initial twenty-one days whileafter attaining enlightenment under the Bodhi tree.
《華嚴》時：為了向那些已超脫世間但尚未證得佛果的有情眾生，揭示宇宙萬法之本質及佛智的至高境界，釋迦牟尼佛在菩提樹下開悟後的最初二十一天，於入定之中宣說了《華嚴經》。

The following twelve years, the level of the Agamas: The beginning of the Buddha's formal preaching to the world. During this level, he mainly expounded on the Hinayana Agamas, which mainly dealt with the "Four Noble Truths," the "Twelve Links of Dependent Origination," "Cause and Effect", as well as the "Force of Karma" that are the basic but relatively easy-to-understand doctrines.
接著的十二年《阿含》時：佛陀正式向世人宣教的開始。這時期主要宣說小乘《阿含經》，涉及＂四聖諦＂、＂十二因緣＂因果法則與業力的基本但相對容易理解的基礎教理。

During the subsequent eight-year was the level of the Vaipulya, the teachings of Theravada Buddhism began to transition to Mahayana Buddhism. The Buddha expounded simple teachings on meditation and mind training through sutras such as the Vimalakirti Sutra and the Srimala Sutra.
隨後八年的《方廣》時，開始從小乘的教理過度到大乘教理。佛陀透過宣說《維摩經》、《勝鬘經》等經來闡述簡單的禪修與修心的教理。

The twenty-two years of the level of Prajnaparamita was after the level of Vaipulya, the Buddha, in order to deepen the understanding of Mahayana teachings for those new to Mahayana Buddhism, elaborated on the meaning of "emptiness" (all phenomena are empty), and through Prajnaparamita meditation (or Zen meditation, an advanced meditation), broke through unreasonable attachments to precepts and other aspects.
《方廣》時期之後的二十二年是《般若》時，佛陀為深化初入大乘者對大乘教義的理解，詳論「空性」（諸法皆空）之義理，透過般若觀（進階的禪修）破除在戒律及其他方面的不合理執著。

During the subsequent eight-year, the level of the Lotus Sutra was the following eight years, also the last eight years that Buddha was life. He found that the foundation on some of the sentient beings were gradually maturing, he preached the Lotus Sutra to enable those who had experienced and practiced the teachings of both Hinayana and Mahayana to achieve Buddhahood. On the last day and night of his life, in Kushinagar, between the twin Sala trees, he preached the Mahaparinirvana Sutra, revealing to the world that all sentient beings possess Buddha-nature, even a person who has severed ties with the Dharma, are protential to become a Buddha.
《法華》時是指再接著的八年，即佛陀在世的最後八年，見到有一部份的眾生根基漸趨純熟，所以說《妙法蓮華經》，讓那些已經歷並能實踐小乘及大乘教法的人能證入聖位，圓滿佛果。佛陀在世的最後一天一夜，在拘屍那拉城娑羅雙樹間，於一日一夜，說《大般涅盤經》，向世間昭示一切眾生皆有佛性，乃至一闡提人（沒有善根的人），也有成佛的可能。

The five levels of Buddhist teachings are like the progression from kindergarten to doctoral studies, corresponding to different levels of doctrine, allowing people of different capacities to find suitable teaching materials for practice.
佛教的五時說教，就像從幼稚園到博士班，對應著不同層級的教理，讓不同根器的人都能找到契合的修行教材。