Mahabharata 3.218.49

श्रीजुष्टः पञ्चमीं स्कन्दस्तस्माच्छ्रीपञ्चमी स्मृताषष्ठ्यां कृतार्थोऽभूद्यस्मात्तस्मात्षष्ठी महातिथिः

śrījuṣṭaḥ pañcamīṃ skandastasmācchrīpañcamī smṛtāṣaṣṭhyāṃ kṛtārtho'bhūdyasmāttasmātṣaṣṭhī mahātithiḥ

Our plain-language meaning of this verse is waiting for scholar review.