Gaudiya Vaisnavas observe all Visnu tattva appearance days along with special fasting. Sometimes these days come next to each other or next to an Ekadasi or Dvadasi tithi which is meant for fasting. This happens every year somewhere in the world for Lord Varaha Dvadasi and Lord Nityananda Trayodasi, but not at all locations due to different sunrise times.
The way Srila Bhaktivedanta Narayana Gosvami recommends to observe these Vaisnava festivals, for example, Ekadasi, Sri Varaha-dvadasi, and Sri Nityananda Trayodasi is as follows:
In countries or cities where the first day is Ekadasi which is suitable for fasting, the second day is the appearance of Lord Varahadeva, and the third day is the appearance day of Lord Nityananda (Nityananda Trayodasi):
In countries or cities where Ekadasi fasting is observed on Dvadasi tithi:
*[Endnote 1 – generally the appearance day of Lord Varahadeva, as with any incarnation’s appearance day, is observed by taking only ekadasi preparations.
*[Endnote 2 – to know the exact time of breaking the fast for your city, please check the Vaisnava calendar.