We humans love order.
OK, maybe not all humans; some people thrive on and take advantage of chaos.
Generally, though, we love order and when it comes to the passage of time, we have tried for millennia to invent systems of organizing it accurately.
That, of course, has practical applications, particularly for purposes of agriculture. And our home, the Earth and the universe, is pretty consistent in providing natural divisions of time that serve our purposes, seconds, minutes, hours, days, years.
Pretty consistent, but not precisely consistent.
Today is Feb. 29, a leap day. A day added to the calendar every four years to adjust for the fact that a solar year, the time it takes Earth to make a complete orbit around the sun, is not precisely 365 days.
It’s also not precisely 365.25 days which necessitates the leap day, so we also have to make another adjustment by skipping the leap day every hundred years, except for every fourth century.
Even that doesn’t do it though. Lesser know that than the leap day, is the leap second. Not only are our solar years not precisely 365 days, our days are not precisely 24 hours. They deviate by milliseconds each day because the rotation of the planet is not 100 per cent consistent and is actually imperceptibly slowing down.
Consequently, a one-second adjustment is occasionally made to Coordinated Universal Time because of differences between precise time (International Atomic Time) and imprecise observed solar time.
It’s complicated, but necessary if you love order.
The Gregorian calendar was established in 1582 to make up for inaccuracies in its predecessor, the Julian calendar. It’s been almost 500 years. If we had not been making those adjustments, Christmas would now be around in early September.
Of course, if not perfect, with the ongoing adjustments, the Gregorian calendar more than adequately serves our purpose of order and has become the standard for business and secular observances worldwide. And you can’t really argue with the science of using the solar year as the basis for it all.
Still, while we love order, we also love tradition and there are still dozens of other calendars in use around the world, particularly for religious observances. These generally, but not all, follow lunar cycles, which accounts for why for Christians Lent and Easter dates change yearly on the secular calendar, just as one example.
There are others though that follow the solar year that are far more accurate than the Gregorian. For example, on the Solar Hijri calendar, also known as the Persian Calendar, Iranian Calendar or SH Calendar, the new year starts at midnight on the date of the vernal equinox and only deviates from the actual solar cycle by one day every 3,236 years.
Whatever calendar we are using, there are scientific bases for most divisions of time. Years (solar), months (lunar), days (planetary). Weeks, on the other hand, are completely arbitrary.
One proposed calendar seeks to address that. The 13-month calendar would mean each month had four weeks and each day of the week would fall on the same dates every year. That only accounts for 364 days, though. The 365th day (and 366th day every four years), would be universal a holiday (hurray!).
It’s a fascinating topic, but ultimately all calendars boil down to convention, a means of organizing our lives. As long as we all (or most of us) agree on the convention it creates the order we all (or most of us) crave.