There is the 25,625 year "Galactic Day" and the 5,125 year "Long Count"(Great Cycle). Both of these are set to END and RESTART on the Winter Solstice of 2012 (11:00 UST Dec. 21, 2012): 

Let's start with the "Galactic Day". As we travel around the Milky Way galaxy, it is my understanding that we do not remain at a constant distance nor at the same orientation in relation to the black hole at its center; a black hole the Maya refer to as the supreme creator, "HUNAB KU". Instead, we move closer and further from this black hole. As we move in closer, we simultaneously become aligned with the Milky Way's equator or "The Tree of Life" as the Maya call it. Upon doing so, we may become exposed to "HUNAB KU's" opposing magnetic forces which would cause our Sun to eject intense solar flares and Earth to experience a magnetic pole reversal (Pole Shift). In the years that we have been furthest away from ,"HUNAB KU", we have been dense low vibrating energy and have been experiencing our dark spiritual years: These years have been part of the "Galactic Night". As we move closer, we become higher vibrating energy and spiritually enlightened beings: These years pertain to the "Galactic Day". We are currently in transition from Night to Day. The complete cycle takes 25,625 years; approximately the same as what modern science has calculated and named "The Precession Of The Equinox Cycle".