Have you picked out your wall calendar for 2007? Are you wed to the calendar view in Outlook or Notes or have you moved your calendar onto the web? Whatever you use, whether it is a DayTimer or a Treo, a 3″x5″ index card or Chopper Girls in Bikinis from the auto body shop down the street, give some thought to imprecision of our calendars.
Marking time is one of the primary forms of standardization in civilization. We can assume the pattern detection of moon phases and seasons by our bipedal antecedents lead to the type of monster calendars evident at Stonehenge, Mystery Hill, and other equinox/solstice calculators which continue to amaze us in their precision. There are two types of astronomical calendars: tropical and synodic. Tropical calendars measure the mean interval between vernal equinoxes — basically Stonehenge-types of calendars. Synodic are tuned to the moon phases and more associated with Islamic calendars. Combined calendars which blend tropical and synodic systems, are associated with the Jewish and Chinese calendar system. From the excellent FAQ on the subject:
“Three distinct types of calendars have resulted from this situation. A solar calendar, of which the Gregorian calendar in its civil usage is an example, is designed to maintain synchrony with the tropical year. To do so, days are intercalated (forming leap years) to increase the average length of the calendar year. A lunar calendar, such as the Islamic calendar, follows the lunar phase cycle without regard for the tropical year. Thus the months of the Islamic calendar systematically shift with respect to the months of the Gregorian calendar. The third type of calendar, the lunisolar calendar, has a sequence of months based on the lunar phase cycle; but every few years a whole month is intercalated to bring the calendar back in phase with the tropical year. The Hebrew and Chinese calendars are examples of this type of calendar.”
The calendar we are now working from in the West — the Gregorian — came about as the church attempted to fix the dates of the major religious feasts, particularly Easter. Wars have been waged over the topic, and indeed if you are Greek Orthodox, December 25 would not be Christ’s birthday — that would come a few days from now on January 6.
“In the sixth century C.E., a monk, Dionysius Exegius, began counting the years from the year of Jesus’s birth, which he miscalculated to be four to eight years later than the actual date. Since Jesus was born during the lifetime of Herod the Great, his birth has to take place before Herod’s death in 4 B.C.E. … so while most Christians celebrate the birth of Jesus on December 25, Jesus was more likely born in the spring — sometime before 4 and 8 B.C.E.”
And to close on a final pedantic point: Leap Year does not occur every four years. February 29 only occurs when the number of the year is divisible by 4 — except in centenary years not divisible by 400. To quote Contrary to Popular Belief: “…the year 2000 was a leap year, but the year 2100, while divisible by four, will not be a leap year because it is not divisible by 400.
Me. I prefer to go lunar and refer to the months, not by their current names, nor the post-French revolutionary conventions, but as the “Harvest, “Wolf” and “Hunter’s” moons. In deference to the need for sophisticated meeting management, I’ll soldier on under the weight of Lotus Notes and hope, somehow, for full synchronization and notification in ’07 on some new handheld device, as my Treo’s days are numbered.