A year can be divided by seven and thirteen and four
Imperfectly factored into two primes and a square
Determined by the motion of the moon and the earth
Leaving one day as a remainder or two in a leap
The seven day week is a natural unit of time
Fitting closely with the phases of the moon
With four weeks approximating the lunar cycle
Though a careful observer sees the slippage
A year spans four seasons of thirteen weeks each
And sometimes contains thirteen full moons
The so-called blue moon making a season with four
Shifted a bit each year by the leftover days
Fifty-two weeks times seven days makes 364
Coming up a bit short out of sync with the sun
Four seasons times thirteen weeks makes 52
Almost but not quite exactly one year
Thus the jokers get placed in a deck of cards
With its four suits of thirteen cards matching up
With our actual seasons and weeks and moons
Drawing arcane cosmology into games of chance
Meaning nothing in the end but still interesting to me
Imagining a calendar that could be shuffled and cut
Arranged into a random timeline distribution
Similar to how some memories play back
If such a calendar could be dealt around in hands
Games based on imperfect information could be devised
Starting with a kind of thought experiment
Envisioning incomplete sets of seven and thirteen and four
Mathematics is quintessentially human
Concepts existing only in the imagination
Constructing proofs of true statements
Numbering our remaining days
