The symbolic shortest amount of time needed to attain enlightenment through intensive anuttarayoga tantra practice. The count derives from the Kalachakra Tantra, which describes how 67.5 deep awareness breaths enter the central channel during each of the 12 shifts of breath from one nostril to the other during the course of a day. The number of breaths that would pass into the central channel during the course of a 100-year lifetime, when divided into a consecutive period of time, would equal three years of 360-day years and three 15-day phases of the moon. The length of the 3-year retreat derives from this calculation.
Tibetan: ལོ་གསུམ་ཕྱོགས་གསུམ། lo-gsum phyogs-gsum