佛祖統紀 3.159

3.159

The commentary states: According to the commentary on the sūtras by Shenzhao: In the month established under the zi cyclical branch, on the day after the full moon, he announced to the assembly the practice of the Dharma. Since this concludes the scriptures, one knows that the preaching of the Lotus Sūtra lasted only seven years. Now, taking into account that it had already opened and revealed, and that both scriptures share the same taste, it is comprehensively called eight years.