At the Lotus Sutra Assembly , Buddha Sakyamuni display the wonderfull array of examples from His Compassionate teaching and leads the Assembly of Vulture Peak to the Samadhi of Lotus Sutra
thus the teaching of One -Buddha Vehicle is born.
The teachings of tientai (Heavenly Platform) is a systematic and detail study on all the teachings of Buddha and his Periods of teaching and
categorised similar to a Sun movement
At Sunrise ,the Sun jumps out of the Mountain from the East
Which Symbolise the first turning of Wheel to the Mahasattva and the Dharmadhatus of Lotus Store Assembly
The Avatamsaka Sutra or Flower Adornment Period
However Buddha Sakyamuni realised the faculties of his disciples are small and seek arhatship
so he began the 2nd period which is the slow progress of the Sun to the 8-9pm position
Which the explanation of 4 noble Truths ,Noble 8fold paths
Next as Sun reaches the Zenith , Symbolise the time is ready for the Mahayana Preaching ,which is Known as Fang1 Guang3 Period
or the Valpuya Period
Next, the Sun reaches the noon period ,which Buddha preach on Maha Prajnaparamita ,the 22 years of Teaching on Emptiness
When finally at 4- 5 pm the sun progress down to the west which Buddha preach to the essence of the One -Buddha Vehicle known as the Lotus Sutra Period
as the Sun comes down to the Sunset position , Buddha started on the Maha Parinirvana Sutra which summarise and reiterates the several essence of his 49 years of Compassionate teaching
http://www.tendai.org/i_tendai_buddhism/history.html