Over millenia, religion, government and kings have shaped the calendar to suit their own purposes, but underlying this is the Earth's regular orbit around the Sun.  Take Imbolc, for example.  Now conveniently celebrated as Candlemas by christians, or Bridey's day (Brigid, Brigette etc) by pagans, even wikipedia states that it falls on February 1st.  Imbolc has been, is and will continue to be one of the eight moots of the year, falling normally on February 4, when the Sun is exactly halfway between solstice and equinox - i.e at fifteen degrees of Aquarius.  And that was this morning, so happy Imbolc.  It is the return of spring, the first green shoots, the first lambs in the fields, the mornings getting lighter.  The fertility is returning to the land, the sap is beginning to rise again.  Much of current new age pagan mythology is just mumbo jumbo, but the celebration of Imbolc, Beltane, Lammas and Samhain as the four cross quarter points has been around for thousands of years and it is hard wired into our systems no matter how much it is misshaped and corrupted by wannabe power brokers.  Remember - we need this planet, it doesn't need us.