Matsya Purana — Cosmography of Śākadvīpa and Successive Dvīpas: Mountains
वेणुका चामृता चैव षष्ठी सम्परिकीर्तिता सुकृता च गभस्ती च सप्तमी परिकीर्तिता //
veṇukā cāmṛtā caiva ṣaṣṭhī samparikīrtitā sukṛtā ca gabhastī ca saptamī parikīrtitā //
The sixth lunar day (Ṣaṣṭhī) is declared to be called Veṇukā and also Amṛtā; and the seventh lunar day (Saptamī) is proclaimed to be called Sukṛtā and also Gabhastī.
This verse does not discuss Pralaya; it focuses on dharmic timekeeping—naming the sixth and seventh lunar days for ritual and vrata observance.
By defining recognized names of tithis, it supports a king’s and householder’s duty to conduct vows, donations, and rites on properly identified lunar days according to Matsya Purana dharma.
Ritually, it standardizes the nomenclature of Ṣaṣṭhī and Saptamī—useful for scheduling vratas and temple/household ceremonies on auspicious tithis in the Matsya Purana tradition.