Write a historical or fictional culture which had a reasonably sophisticated way of reckoning time: a calendar. Some possible suggestions: the Julian calendar (of the Romans, named after Julius Caesar); the traditional Chinese calendar; any of the Hindu calendars of India; any of the Buddhist calendars used in Southeast Asia; the Hijra calendar (used by many Muslims); the Hebrew calendar; the Korean calendar; any of the traditional Japanese calendars; the ancient Egyptian calendar; the traditional Ethiopian calendar; the pagan/neopagan Wheel of the Year; any of the astrological calendars; the Zoroastrian calendar. If you choose the Mayan calendar, be aware that it is somewhat complicated, and there is only speculation as to what the tzolk’in might be used for. Give me that speculation and discuss its astronomical implications.
Write a short essay of at least a single-spaced page in 12-point font (or two double-spaced pages) about how your calendar relates to the sky. You should address:
how the calendar you have chosen is connected to the motion of the Sun, the stars, the Moon, and anything else of note. Describe how and how well do they line up with the days, months, years, or whatever else the calendar has.
which motions in the sky are treated as more important, and which are treated as less important
how your calendar accounts for the fact that the Earth’s rotation, the Earth’s orbit, and the Moon’s orbit don’t synch up well. I described what effects this has in the Gregorian calendar above; tell me about the one you have chosen.
any “intercalary months” or leap-whatevers needed to keep your calendar in sync with the various celestial cycles, why they are needed, and how they work
what celestial events your calendar’s reckoning predicts exactly, and which ones are only approximate (for instance, the winter solstice is sometimes 21 December and sometimes 22 December in the Gregorian calendar, because we consider the daily rotation of the Earth to be more important than the exact moment that the axis of the Earth’s tilt is maximally toward or away from the Sun.
You might also write about:
How are the dates of holidays or religious observances reckoned in your calendar? Are all of them the same? Why or why not? (For instance, Easter moves every year but Christmas doesn’t. Why is this?)
Are there any particularly interesting features of your chosen culture’s traditions, geographical origin, or history that inform the calendar, especially those that connect to the stars?
What are the historical ancestors of your calendar (for instance, the Gregorian calendar draws inspiration from the Julian calendar)?
How has this calendar adapted to the modern world?
For example, the Gregorian calendar, the calendar we use, has the following properties:
The smallest unit of time on the calendar is the solar day, judged by the motion of the Sun in the sky
We also have the month and the week, which are based on the Moon. The month is an approximation (but is not exact, not even on average) of how long it takes the Moon to cycle through its phases; the week is an approximation (not exact) of the amount of time it takes the moon to make a quarter-phase.
The week is partially based on the Judeo-Christian religious tradition, which asks people to work and rest in seven-day cycles. The names of the days vary from language to language; in English they come in part from the names of Norse gods.
The year is the seasonal (tropical) year, based on the solstices and equinoxes.
These things don’t quite line up. There isn’t an integer number of solar days in a seasonal year, so we need leap years. There isn’t an integer number of lunar cycles in a solar cycle, so our months are not exact. Finally, a lunar month isn’t exactly 28 solar days, so the week is not quite one-quarter of a lunar cycle.
We give a great deal of precedence to the cycles of the Sun, reckoning dates only by their distance from the solstices and equinoxes, and do not really care about the cycles of the Moon that much. That is, a holiday falling on December 25 will reliably occur 3-4 day after the Winter Solstice. There is no attempt to make the lunar cycles line up with the solar ones.
The names of the months mostly come from Roman gods and emperors.
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