CULTURAL SENSE

The story of our calendar and why it is rife with anomalies

- JAMIE TAN AND SUMIT NAG

An earth year, viewed through an astronomical lens, can be dumbed down and defined as the time that it takes for the earth to make one complete revolution around the sun. Eminent astrophysicist and science communicator, Dr Neil deGrasse Tyson, explained the matter on his podcast, Startalk, with a lot more precision saying first that when we ring in the new year, Earth is always six hours behind the completion of one trip around the sun. Rather than deal with these six-hour increments, we just cleanly divide the year into whole [24-hour] days. The engineered symmetry of days requires that at some point in time, we account for rounding down.

“The earth’s orbit around the sun doesn’t care about how long it takes Earth to rotate on its axis. But we do, so we’re shoehorning our days with respect to how long it takes Earth to go around the sun. But wait [there’s more]. A year for us is the time that it takes the Sun and Earth’s relationship to repeat in such a way that the seasons stay attached to the months of the year we’ve given them to. Our year is based on a seasonal calendar because we’re [human civilization] historically agrarian. The seasonal calendar is slightly different from the time it takes the Earth to return to the same spot in its orbit. We simply don’t use that calendar. That’s called a sidereal year, where we match up with the stars that surround the sun. But our seasons don’t match up with the stars. And stars [themselves] migrate through the year, Spring will always be in March [for the Earth’s northern hemisphere] but the sky you see in the springtime in March will shift against the calendar because that’s not the [type of year] year [sidereal year] that we’re based on. Whatever [type of] year that you’re based on that repeats every year, other accountings will then shift relative to it.”