As we are moving more and more into the eternal Now and natural/universal law it seems only natural then that it would be the way to go to move beyond the 12 month Gregorian calendar construct upon which our 3D earth society is based.
Much is spoken of the Traditional Mayan Calendar of 12 Keys/Codes, which Drunvalo Melchezidek expounds,  but little is heard of the Mayan Dreamspell 13 Moon Calendar -  aka Nature's calendar based around the natural flow of the 13 moons
Here is are great piece explaining this
NATURE'S CALENDAR:  http://www.13moon.com/time-is-art.htm
Also here is a great article giving an explanation of the difference between the two Mayan Calendars.
http://www.13moon.com/not_the_mayan_calendar.htm
Personally I am leaning towards the 13 Moon Nature's Calendar.
Enjoy
Elizabeth