Final answer:
The duration of the floodwaters on earth is not explicitly mentioned in the historical accounts.
Step-by-step explanation:
The duration of the floodwaters on earth is not explicitly mentioned in the provided information. However, the flood was said to begin its rise on the night of the Feast of Saint Michael (Id Mīkā'il), on the twelfth day of the Coptic Month of Ba'una (June 20). It is important to note that this information is part of historical accounts and may vary in different sources.