Since the new and full moon has long been known to effect human judgment and behavior, it has been the tradition of Ashtanga Yoga practitioners to refrain from practicing during these phases of the moon's cycle. In order to observe this practice, we need to understand the relationship between three celestial bodies; sun, moon and earth. Gravity is the most popular belief of the combined effects of this subtle but ubiquitous force that fluctuates throughout the phases of the moon. Ocean tides are the best example of a gravitational effect.
Since our bodies are made up of about 65% water, it would make sense that body fluids will respond to the same forces that generate the tides. This internal tide is believed to be responsible for connective and emotional changes that are known to occur during the new and full moon. Yoga East's moon calendar is calculated in accordance to our time zone, moon phases and tidal charts.
The last new moon of December is the 29th.