|The concept of axial precession|
The graphic to the left depicts that phenomenon, described as "Precessional movement of the Earth. The Earth rotates (white arrows) once a day about its axis of rotation (red). This axis itself rotates slowly (white circle), completing a rotation in approximately 26,000 years" (ibid).
The phenomena of axial precession and axial tilt are important for civilizations to take into consideration in their long range planning.
Or for that matter any planning that is based on ecological / environmental phenomena that have a meaningful impact on civilization.
One calendar that does so is the Mesoamerican Long Count Calendar since it has a method of synchronizing with axial precession as follows:
1 Day = Kin (keen)(see e.g. Mayan Long Count, and Mesoamerican Long Count). We can calculate how close the Long Count Calendar is to the axial precession cycle:
20 Kin = 1 Uinal (a.k.a. Winal)
360 Kin / 18 Uinals = 1 Tun (toon)
20 Tuns = 1 K’atun (k’a toon)
20 K`atuns = 1 Baktun (backtoon)
Earth's axial precession = ~25,765 years(see e.g. Precession of the Equinox). Therefore, the 26,000 Tun figure is within about a half of one percent of being equal to one complete cycle of the Earth's axial precession as calculated by other astronomical means (we don't know which of the two is more accurate, but a ~0.54% variance between the two is not significant).
26,000 Tun * 360 Kin per Tun / 365.24 solar days = ~25,627 years
25,765 years - 25,627 years = 138 years (axial precession variation)
138 is ~0.54% of 25,765 (very slight degree of variation)
[Note that current calendars of civilization do not even take axial precession into consideration at all.]
Another factor of the Long Count Calendar is that "Thirteen b’ak’tuns made up a Great Cycle, which adds up to 5,200 tuns" (Mayan Calendar Portal).
So much was falsely made about a "Mayan apocalypse" on December 21, 2012, because it was the end of a 5,200 Tun Great Cycle (the next Great Cycle of 5,200 Tuns began on the next day, December 22, 2012).
Anyway, that Great Cycle concept is an additional helpful factor because the 26,000 Tun cycle is segmented into five Great Cycles of 5,200 Tun each (5,200 x 5 = 26,000).
Since five Great Cycles make up one 26,000 Tun cycle, and that equates to one cycle of the axial precession of the Earth, we can segment the cycle of axial precession into five segments or sections of time using The Long Calendar.
Why does any of this matter, and what does it have to do with a good or bad calendar, in terms of long range planning by civilizations?
The first factor to consider is the axial tilt:
The Earth's axis remains tilted in the same direction with reference to the background stars throughout a year (throughout its entire orbit).(Wikipedia, Axial Tilt). Next consider what happens when the axial tilt rotates during the cycle of axial precession:
This means that one pole (and the associated hemisphere of the Earth) will be directed away from the Sun at one side of the orbit, and half an orbit later (half a year later) this pole will be directed towards the Sun.
This is the cause of the Earth's seasons.
Variations in Earth's axial tilt can influence the seasons and is likely a factor in long-term [non-anthropogenic] climate change.(ibid). Thus, the Long Range Calendar would divide the 26,000 Tuns into five segments of 5,200 Tuns each, which would give such a calendar the utility to help civilizations determine when and how ecocosmological climate change, i.e., natural cosmic climate change would take place in the different hemispheres of the Earth.
Why is that important?
Because it would tell, among other things, when polar ice caps would naturally melt to cause natural sea level rise that would flood coastal areas, when the poles would naturally ice over to again cause natural sea level drop once again, how the flora and fauna would begin to adapt as those climate changes gently and slowly began to take place, as well as many other fundamental things civilizations need to know to happily survive on a planet like the Earth (see e.g. this and this).
Wise civilizations would use a long term calendar for long term planning in terms of zoning, when and where to build, when and where not to build, how to build for the current and next cycle, and therefore how to avoid a lot of waste, destruction, loss of life, as well as avoiding great, unnecessary expense.
[This all assumes that any Earth civilizations would not cause anthropogenic global warming induced climate change, as current civilization already has done, to a very reasonably predictable Earth environment.]
In closing, let me say that that this post emphasizes the utility of the Mesoamerican Long Calendar, but more than that, it makes it obvious how unwise the current civilization is to always assume that older nations, peoples, and eras were inferior to us in wisdom, vision, and intelligence.
Video shows ~26,000 Tun / Year axial procession cycle: