Nature doesn't recognise time, days, weeks or years; those are merely things we've created to time-keep.
Classic deepity. Nature doesn't speak in terms of our chronological labels, but it does follow regular cycles that we name and predict. Earth does complete a rotation once a day and a revolution once a year. Old Faithful does erupt about every 90 minutes. It is not unreasonable to predict some natural disaster according to our own time scales, because those time scales are based on nature's.
(The 2012 hysteria is indeed a load of crap, but be careful not to overstate things.)
However, the fact that nature adheres to seasonal events and natural disasters that occur predominantly in some places and with predictable intervals when looked at in terms of millennia, does not in any way suggest humans are able to improve upon those cyclically occurring natural events by making predictions based on their own calendars. Making a calendar to run in tandem with nature is all well and good, but using it to predict events is utterly inane.
If you make a calendar to fit nature's regular timescales, then the two methods are one and the same, except the calendar has handy labels that we can convey with language.
The problem with the Mayan calendar basis for 2012 hysteria is not that it was a human calendar, but that it ended at an unremarkable point due to the religious beliefs of those who crafted it.