The Vaishnava calendar is calculated by His Divine Grace Mahamamandaleshwar Mahant Krsna Balaram Swamiji, who appeared in and was raised by an enlightened Gaudiya-Brahmana family, descending from Kasyapa Muni, in the holiest land in India, Sri Vrindaban Dhama. He is expert in Vedic knowledge and holy astrology. He annually calculates the Vaisnava Calendar telling the proper Holy dates and Ekadasi dates. This calendar is calculated with exact agreement with the ancient scripture Haribhakti Vilasa of Srila Sanatana Goswami, a direct disciple of Lord Chaitanya Mahaprabhu.
It is incumbent upon every follower of Bhagavat Dharma Samaj to abide by this properly astrologically calculated calendar following the exact system of the Haribhakti Vilasa. There are two systems of Vedic astrology — Solar calculation and Lunar calculation. The Vaisnava, devotional lineage, follows the Lunar calendar to calculate the exact Tithi (the lunar day). There are twenty-seven constellations and they travel with the moon. As the moon travels, the Tithi is carried by the moon. Therefore, the Vedic calculation of religious dates works per the position of the moon, and not according to the geographical position of a particular country. In spiritual life, knowing the proper calculation of the Tithi is more important than observing it.
In our Vaisnava calendar we carefully follow all the required Vedic rules for calculating the Ekadasi Fasting dates so that the Ekadasi observer receives proper and sufficient merits from the fast.
[Hari Bhakti Vilasa/Bhramanda Purana, sourced by Sri Krsna Balaram Swami]