Our twelve month calendar might be the world’s oldest information data structure, save language itself. And it shows its age. How does it go? “Thirty days has September, April, June and November, all the rest have 31.” Except February, with 28 or 29 days. The number of days in a month varies and our seven-day week does not coincide with our months. Even if you know the date, you still have to ask the day of the week. There is an arguably better way, though it is probably too late to change.
Our calendar comes from the ancient near east as modified by the Romans and later by the Christian church. The Babylonians liked to divide time by twelves (or by 60, which is just five 12’s). Our hands have ten fingers which is divisible into halves (two hands, right?). But not into thirds or quarters. So the Babylonians did not choose a base-ten system, leaving it to their Islamic decedents to invent our current decimal numbers thousands of years later. Instead, they chose 12, which can be divided by 2 and by 3 and by 4.
Sixty is even better; it divides by 2, 3, 4, 5 and 6. That is why our clocks have 12 hours and 60 minutes per hour. And that is one of the reasons calendars have 12 months. The other being that there are roughly 12 full moons in a solar year of seasons. Want to know a quarter of a year? Its easy because twelve evenly divides by four into three-month seasons. Later, when time keeping technology advanced, the day was similarly divided into 12 hours, making it easy to know what that a half day is 6 hours, a third of the day is 4 hours, and a quarter day is 3 hours.
The Babylonians and their Semitic brethren (including the Jews and the Arabs) used a strictly lunar calendar. Months always began on a new moon and the full moon always fell on the fourteenth or fifteenth day. But there are not really twelve months in a solar year. A lunar month is 29.53 days. (That is not quite the time it takes the moon to orbit us since we are also moving around the sun. So it is the time the moon takes relative to our view of the sun.) Twelve times 29.53 is about 254 days, eleven short of the 365.242 day solar year.
Measuring months by new moons was nice, but keeping the calendar aligned to the seasons was a life-and-death necessity for agricultural societies. So they would add an additional month once every few years to get the calendar back on season. The Jewish calendar still works that way, which is why the dates of Jewish holidays vary from year to year. They are fixed on the Jewish calendar (and often fall on the full or new moon). They only vary on our standard Julian calendar.
Modern days start at midnight, but only because we have good clocks. Ancient peoples started their days on the only reliable clock they had, the sun. So days began at either sunrise or sunset. The Jews choose sunset, which is why Jewish holidays start the night before their date. They don’t really. The “day” just begins at sundown and the holiday ends at sundown the next day. Except that strict lunar months required accurate moon sightings in the days before precise orbital calculations. Out in the sticks, there were no priests trained in sighting the precise new month. And there were no telephone lines to Jerusalem. So to be safe, the outlying provinces celebrated most of the required holidays for two consecutive days each, assuming one would be the right day officially at the central temple. The USA is definitely the sticks from the ancient Jewish perspective, which is why observant Jews are away from work for two days (plus one evening) for most holidays.
The Romans and their Christian decedents changed the ancient lunar calendar to a more solar centric one. After all, the sun was on of their gods. The “Julian” calendar is named after Julius Caesar, who finalized our current months in 46 BC, naming one (July) after himself. It was then that the 29 day February leap every four years was devised. That makes the average year 365.25, which very close to the actual value, 365.242 (and a little). It was not until the Renaissance that the error became apparent and Pope Gregory XIII decreed the refined “Gregorian” calendar with one less leap year every 100 years.
But the Jews (or possibly their Semitic forebears) added one other vital calendar concept, the week. The Bible decrees a seventh day of rest and most of the world now practices this. The various religions cannot agree on the day - the Jews say Saturday (and they invented the concept, right?), but the Christians moved it to Sunday (probably a concession to Roman Sun god worshipers) and Islam uses Friday. Plus a lot of peoples have inflated it to two days of rest. The result of this is that we have overlaid seven days of the week over the old monthly calendar, with confusing results. Plus for religious and work-related reasons, the seven-day week is a lot more important to our lives than other calendar issues.
A Better Calendar
If we don’t require a lunar month (and every since the Romans, we have not), then why not make months exactly four weeks? That would mean that every month would start on Sunday the 1st (or whatever other day you might choose). If it is the 8th it must be Sunday again and the 10th would always be Tuesday. Much easier, right?
By a lucky coincidence, there are almost an even number of four-week months in a solar year. Four times seven gives us a 28 day month. And thirteen such months is 364 days, only 1 or 2 days shy of the actual solar year. Of course, being superstitious, 13 months per year sounds scary. Though it would give us an extra month to name after someone. (My recommendation would be a new month named “Steven”.) And 13 months does not divide into four seasons (or even in half for that matter). But by another lucky coincidence, there are an almost even 13 weeks in a solar season. So in my new fantasy calendar, there would be two four-week months and one five-week month per season. Every third month (say March, June, September and December) would be an extra week long, giving us a little more time to get those end-of-quarter reports out.
That gives us 12 months a year, each with exactly 28 or 35 days, where the days of the week always fall on the same dates. If you know the date you also know the the day of the week, a very nice feature for our modern week-centric society.
But what about the extra 1.242 days in the solar year? So far we have 52 weeks and 364 days in our year and we need 365.242 and a bit. You will like the solution, since it involves a new holiday (and sometimes two). Under my “Stevian” calendar, there would be an extra “New Year’s” day, where we begin celebrating the new year without work. And without even a day of the week, since Saturday, December 35th would be followed by “New Year’s” (call it New Year’s 1 or “Sunday, December 36 if you like) followed by another Sunday, January 1. And every four years, there would be an extra leap-year holiday, giving us two consecutive “Year’s End” days (call them New Year’s 1 and New Year’s 2, or maybe Sunday, December 36 and another Sunday, December 37 before a third Sunday, January 1.) Following the Gregorian tradition, every 100 years on dates ending with “00”, there would not be an extra second leap-year holiday.
Or Maybe Not
Great system, right? It’s simpler to use and gives us a new holiday or two. The only problem is figuring out when your birthday falls given you were born under the old calendar. Conversion of old dates would be a chore. And if you thought the Y2K computer software meltdown non-event was scary enough, that would be nothing compared to updating our systems to cope with my Stevian calendar.
Plus without doubt, the religious world would stick to their old calendars. They may not be cast in concrete but, worse, are cast in the Bible. So not only would the Jewish and Islamic holidays be confusing, but the Christian holidays would be too. When is Christmas this year? It would take a priest to know. Worst of all, the religious day of rest would vary from year to year as well as from religion to religion. The extra New Year’s pseudo-Sunday would shift the ancient seven-day cycle by one or two days each year. When is the Sabbath this year? Check your calendar.