Vishweshwara-samhita - Chapter 16 - Verse 41

The worship of Lord Viṣṇu on the Aśvayujī (Aśvayuja) Śukla Navamī (the ninth day of the bright fortnight of Aśvayuja) is said to grant all desired results. Specifically, the worship on Adivāra (the first Tuesday of the month) and on Chaturdaśī (the fourteenth day of the lunar month) during the Krishna Paksha (the dark fortnight) is considered particularly auspicious.