Dhanurmasam Starts Dec 16th to Jan 14th
This period of month is considered as highly auspicious for Vishnu devotees. Old Hindu scriptures have set apart this month to be completely focused on devotional activities. Other non-devotional activities (such as weddings, purchase of property etc.) are prohibited during this month so that attention can be given exclusively to the worship of God without any diversions. In South India, especially the Vaikunta Ekadasi, which falls during Dhanur Mas, attracts thousands of devotees. Temples conduct special pujas during this period.
Sri Krishna in Bhagavad Gita, says मासानां मार्गशीर्षोहम् 10.35. I manifest more in Margashirsha Maas among the different months in a year.
According to tradition, the Gods wake up early in the morning during the month of Dhanurmas. They perform special prayers to Sri Maha Vishnu during the auspicious period of “Brahm Muhurta”, which is one and half hours before sunrise. During this month, devotees offer prayers to the Lord very early in the morning. The month of Dhanurmas is considered a very special month for performing Puja of Vishnu.
Dhanurmas Phal Shruti: Worshiping Vishnu on a single day during this auspicious period is equal to worshiping Vishnu with devotion for 1000 years. Every single step taken towards the nearby lake, river etc. for morning dip during this month brings forth merit equal to performing an Ashvamedha Yaga.
During this period the sun is in the Sagittarius or “धनु राशि”,the period when the sun passes from Sagittarius to Capricorn or “मकर राशि” is considered as a period of scarcity to the plenty in India. Feeding or giving alms to the deserving poor and Brahmins during this period is believed to confer great merit i.e. Punya.