For the human race, having a "calendar" was the most natural thing in the world.
Humans had innate biological clocks, and those clocks matched a planet's rotation perfectly—perhaps for creatures living on the surface, such rhythms were more conducive to foraging. Or perhaps conversely, their foraging behavior had formed a selection mechanism over the course of evolution. In any case, by the time people evolved the advanced entertainment function known as "consciousness," the "rhythms" they possessed had already been bound to the alternation of day and night.
This was the most natural unit of time—"day."
Beyond that, there were "months," produced by changes in a satellite's shadow, as well as "seasons" and "years," caused by the changing duration of sunlight brought about by axial tilt.
The only problem was that these units did not mesh very well. For instance, one sidereal year in Divine Land was roughly three hundred and sixty-five and one-third days, while one sidereal month—one complete cycle of lunar phases—lasted twenty-seven and two-fifths days.
Unless someone was willing to use a calendar with 13.33327 months per year and 27.4 days per month, there was no way to blend a natural lunar calendar and solar calendar together.
That clearly went against intuition. A purely lunar calendar was also difficult to use for guiding farming, while a purely solar calendar was hard to reconcile with the phases of the moon.
Only over the course of its long history had the human race of Divine Land developed the great invention known as the "lunisolar calendar."
In other words, the concept that "a month has thirty days," so taken for granted by modern humanity, had not actually been so self-evident in the past.
Divine Land possessed "natural rhythms," a "star," and "a single satellite" to define its calendar. It was practically