Dhanur Masa or Dhanurmas is a month in the Hindu calendar. It corresponds to the zodiac sign of Saggitarius (Sun transits through Saggitarius). The Dhanus month or masa is called Margazhi (Margali) in the Tamil Hindu calendar. Dhanurmasa is also called as Shoonya Masa as it is considered inauspicious to do any good thing other than God and Holy functions.
During this month, devotees offer prayers to the Lord very early in the morning. The month of Dhanurmasa is considered a very special month for performing Puja of Vishnu. Vishnu Sahasranama is chanted during the period.
The 30 pasurams/verses of Thiruppavai will be recited to wake up Lord Vishnu. Thiru means Sacred and Ppavai means Vrat. It is believed that Goddess Goda Devi, also known as Andal has composed Thiruppaavai in an old Tamil poetry writing style. She lived in Srivilliputhur, now in Virudhunagar district of Tamil Nadu in 9th century.