20 March 2009

Of Seasons and Calendars On The Vernal Equinox

Spring begins this evening, when the vernal equinox occurs. Astronomy doesn't define it exactly this way, but basically, this is the day when the period from sunrise to sunset is as close as possible to twelve hours. Days will continue to get longer until the first day of summer.

March used to be the first month of the year, in line with the beginning of Spring, a fact still reflected in month names like October and December for the 10th and 12th, as opposed to the 8th and 10th months of the year. I don't know precisely when this transition took place, although I've known in the past and could look it up.

Starting the year in the Spring makes a good deal of sense if you are basing your calendar on the Northern calendar seasons. In Spring growth starts and animals have babies. Winter proceeding it is a dead period. Spring is at the beginning of a tree ring, while winter is at its end.

Honestly, I've also never figured out why our solar calendar doesn't reliably start and end on or very near some solstice or equinox. If we were going to start the year roughly when we do now, for example, why not start the year on what is now December 21st?

I suppose that it is nothing more than path dependence (i.e. we stumbled into centuries ago, it not fully knowing what the consequences would be when the system was set up) and the notion that it is more important for calendars to be consistent than in touch with the astronomy and the weather. An adjustment was made around the time that George Washington lived to match up astronomy and the calendar, but apparently that was such a bad experience that the world is in no rush to repeat it.

Then again, one notable effect of this is that business quarters are out of sync with the seasons, which may be intentional. Starting the first business quarter in January makes great sense in the retail industry, where the year typically concludes with a big Christmas shopping season that accounts for much of the year's sales. If Christmas were honored a few days into the first quarter, rather than a few days before the first quarter, quarterly accounting reports would be much less useful.

The fact that our year now begins in January rather than March is, in part, symbolic of the ascendancy of commerce over agriculture in our economy.

On School Calendars

Conveniently, spring break in the Denver Public Schools starts this afternoon, right in sync with the season.

Presumably, the reason that the academic year starts in the autumn, rather than the spring, is that the longest break from school of the year rooted historically, and largely anachronistically, in the need to have children at home helping on the farm, is summer vacation. The period from fall through the spring is the longest period of time uninterrupted by a school break of more than a couple of weeks, so it makes administrative sense to start the school year there.

There are now a few schools in Colorado that operate on year round calendars, in an effort to respond to the fact that fewer than 2% of the population now lives on farms where the traditional justification for summer vacation makes any sense, and that the percentage is far, far smaller in the urban school districts that the vast majority of students attend. Instead, these schools have breaks spaced more evenly throughout the year. The long interruption of regular instruction during summer vacation means that teachers and students must spend considerable time in the autumn getting back up to speed on curricular content learned in the spring and forgotten over summer vacation. This is the evil most schools are trying to address with their no extended summer vacation schedule.

In an era where a large percentage of kids have two working parents, summer vacation can be a burden, rather than a help to families. It has created a cottage industry of summer camps with many kids going from one to the other for most of the summer. For kids whose working parents can't afford day care or summer camp and don't have relatives out of the work force, summer vacation means weeks with little or no adult supervision at all. Indeed, quirks like summer vacation, "late start days," teacher development days, relatively short school day schedules and the like are an important reason that a large percentage of homemakers make their choice, rather than choosing to enter to paid workforce.

This has major economic implications. Decisions about how long someone will spend as a homemaker are a major component of gender discrepencies in earnings. Years not spent in the work force while caring for children have a major impact on the lifetime earnings of women, because pay is strongly corrolated with seniority, especially for more knowledge based work, and each year spent out of the work force reduces reduces the number of available years at the end of one's career when one has reached late career peak earnings. The free child care provided by the public school system during the school day by freeing up parents to work at least part-time without hiring child care on an expensive private basis for a small number of children leaves families without pre-school children, on average, better off economically than one might expect, compared to families with pre-school children. Families get quite a bit more than simply freedom from having to pay school tuition in the public education deal economically. Indeed, some of the positive impacts of programs like Head Start, one of the consistently most praised government programs, may simply arise from the fact that they make it easier for families to support themselves economically and escape poverty with employment. Seemingly mundane administrative decisions, like school year schedules, have strong and measurable macroeconomic and distributive economic effects, and effects on issues like how many children a family will choose to have, simply because they have such a great impact on the economic structure of households.

Public school schedules may have greater economic impacts than objects of much greater study by economists and economically minded scholars, like contract law rules, tax benefits associated with having children, and interest rates. While quite a bit of study has been devoted to the individual economic impact of education on the people who receive it, relatively little study has been devoted to the economic impact of education institutions as a whole on how households are structured, which in turn impacts how economic activity is structured. But, major unheavals in the structure of the economy and the role of women in our society since the 1960s and 1970s have made a simple reliance upon tradition to reach the right result on these issues disfunctional.

The modern benefits of summer vacation are mostly not particular to summer. Many children of divorced parents who live great distances apart from each other spend the school year with one parent, and most of summer vacation with the other, with other breaks divided, and this works out better logistically when there is one big long break. Summer vacation is also convenience for school teachers who want to pursue graduate degrees, given them a big block of time to take additional courses. There is a common sense and sentimental attachment to the freedom from school year structure and opportunity to explore something different that a long break provides. And, the mere fact that most kids of school age (and most college students) get long summer vacations, impacts how the economy organizes availability of entertainment and camp options for kids, and the entire family tourism industry. Early adopters of an alternative schedule often are disadvantaged simply because they are out of step. In the same vein, I suspect that one reason that the Denver Public Schools is one of the first to get out in the spring (generally just before Memorial Day) is that there students through their parents value an opportunity for their teens to get a first shot at summer jobs for which many suburban teens will not be available for an additional week or two.

Conscious awareness of the current impacts of summer vacation on families, good and bad, could help us foster an educational system that is better integrated with a modern economy, and the kinds of families that we have today. While curriculum reform hasn't made a lot of progress since classical languages were dropped in the 1950s in favor of subjects with more modern relevance, the administrative traditions of schools are also basically stuck in a rut rooted in assumptions that haven't made sense since the Baby Boom.

Seasons and Weather

I've also wondered more than once about, but never seriously investigated, the discrepancies between seasons delineated by astronomical events, like the equinoxes and solstices, and seasons delineated by weather phenomena that vary within narrow boundaries from year to year, both randomly and in accordance with location and man made phenomena like global warming.

For example, one could have a perfectly serviceable definition of the "cold season" as the period that runs from the first frost of the autumn to the last frost of the spring, and there are purposes in gardening and farming for which concepts like this, such as the "growing season" are used. Indeed, the group of amateur naturalists who have kept consistent records of these kinds of events for their own fancies are now highly sought after by scientists and being coordinated by an internet site, in order to better understand climate change, a novelty in an age where amateur scientists have largely been replaced by professionals in universities, in government and corporate labs, and in consultancies. These are the sorts of seasons that groundhogs tell us about and that are referred to when one casually describes New Zealand as a place where it is summer all the time, or Northern Siberia as a land of endless winter.

My intuition is that the weather we associate with spring generally appears earlier than the vernal equinox, which may explain the calendar discrepancy, and that the same is true in other seasons. But, I've never sat down with average daily temperature and precipitation charts and figured out where the lines between the seasons would would be drawn if they were based upon weather, rather than sunlight.

Still, for all the flaws of our calendar makers, I have to give them credit for being more optimistic than the Mayans, whose calendar just quits at 2012.


NewMexiKen said...

5:44 AM this morning MDT (11:44 UTC).

Mishalak said...

It was the Romans who changed us over to January 1st as the start of the year. The change was gradual and probably political as well since prior to the Julian Calendar reforms the inserting or failure to insert an extra intercalary month was often done to either lengthen the office of friends or shorten the length of office of enemies. It is not recorded if the change in the date of the new year, also the date of changing over office holders in the Republic, was done to get rid of people they did not like, but I would guess it was.

Sometime before Julius Caesar introduced the new calendar January 1st was already the date of the new year. And it was celebrated as such in England in the mdidle ages, but March 25th was apparently the start of the _legal_ year until 1751 in England.

Pretty much everybody adopted January 1st as the start of the new year with the adoption of the Gregorian Calendar.

Kevin Dickson said...

My theory about a long summer break for north american city school systems has to do with the HVAC systems. Air conditioning wasn't available when these schools were built, but steam boiler technology was quite common. Consequently, there was no school during the time when comfort was hard to provide.

Scott Yates said...

Speaking of DPS and calendars, I blogged about DPS' inability to make a decision about the calendar, and also the inability to make a useful calendar.

I didn't just want to be a rock-thrower, however, so I made a useful DPS calendar.

And while I'm at it, allow me to plug the candidacy of a great guy to fill the HD3 seat that became available: Sam Cassidy.


Andrew Oh-Willeke said...

I was about to make a post on rock throwing, but not the political kind. Maybe I'll get around to it.

Andrew Oh-Willeke said...

The book "Outliers" also suggests that there are stunning significant birthday effects on academic performance in most countries that flow from the school calendar.