This is the discipline on this list where the distinction between the living tradition and the Western product is sharpest, and it should be stated directly.
The Tzolkin is still kept. Daykeepers, ajq'ij, in the Guatemalan highlands among the Kiche, Kaqchikel, Mam and Tzutujil maintain an unbroken day count, conduct ceremonies on appropriate days, and read birth days for the people who consult them. That count is continuous and the practice is a functioning part of Maya religious life, currently undergoing a public revival after decades in which it was practised quietly through the Guatemalan civil war and the violence against indigenous communities that accompanied it.
Alongside it, and not connected to it, sits the Dreamspell or Thirteen Moon calendar devised by Jose Arguelles and published in 1990. It uses the twenty signs and thirteen tones and looks like the Tzolkin, but it runs on a different correlation, adds a leap-day rule the Maya count does not have, and therefore gives a different sign for the same birthday. Its vocabulary, galactic signatures, the Harmonic Convergence, tones of creation, is Arguelles's own synthesis. Guatemalan Maya elders have objected publicly to it being presented as Maya.
The 2012 episode belongs here too. The end of the thirteenth baktun of the Long Count on 21 December 2012 was a calendar rollover, comparable to an odometer, and Maya inscriptions themselves refer to dates far beyond it. The apocalyptic and transformational readings attached to it in the West came from Arguelles, Terence McKenna and a large popular literature, not from Maya sources, and Maya organisations said so at the time.
Anyone approaching this discipline commercially should know which count they are being sold.