There is not a single calendar used by the Maya, there were several. The tzolkin is the augury calendar, the haab is their solar calendar, and the Long Count is the one with the rapidly approaching end date. And there were other minor calendars and cycles they kept track of over the centuries.
There is no problem with the tzolkin. It ends every 260 days (less than nine months) and a new one starts, just like our calendars. The end-date for this calendar is nothing to worry about.
The haab likewise begins anew at the end of every year without dire circumstance.
The “Calendar Round” is a larger calendar cycle. The tzolkin and the haab run in parallel and end together on the same date every fifty-two years. This marks the time when they usually had their fire ceremony: putting out the fires in all the surrounding villages and waiting until the dawn, the appearance of the Sun again, to start a new fire in the city and carry the new flame to all the countryside. Apparently, they feared the Sun would not return that night. But why?
That still leaves us with the Long Count. Where did it come from? And for what purpose would they need to keep track of such long periods?
According to most theorists, the creators invented the calendar in the second century BCE and simply ‘back-dated’ the beginning from some mythical point. Some claim it dates from the birth of the planet Venus.
Jenkins and others think it was nothing more than the first rising of the planet Venus following some other event, as yet undiscovered. It seems like a rather lame start of an exhaustive enterprise to back-date the start of the Long Count to something so minor. It would lead one to believe that the ending of the calendar will be something as equally insignificant.
The Maya also understood precession of the equinoxes. This is the slight wobble of the pole of the planet which moves at a certain rate. The North Pole currently points at Polaris, the North Star, and in the past pointed elsewhere; in describes a circle in the sky over a period of about 26,000 years. But why is precession important? Other than show the mechanics of our rotating world in the cosmos, does it actually do anything for us?
Some theorize that the precessional cycle is a major cycle the world goes through. Although the numbers do not match up with any culture’s mythology it is an attractive idea.
But since the Maya understood precession, why didn’t they say the Long Count was aligned in some manner to the precessional cycle. Unfortunately, they do not. That is the idea of modern theorists on the subject.