On leap day 2024, Philly will make up for 1,440 minutes of lost time

During the 2.3 billion miles the spinning Earth has traveled around the sun in the last four years, the clocks of the world have quietly banked about 1,440 minutes.

On Thursday, we get to go to the cosmic ATM of time and make our quadrennial withdrawal — that 24 hours that constitute “leap day,” as the shortest month in the shortest season gains an extra day and the rest of calendar takes a forward “leap.”

How we got here is quite the astronomical saga, and enjoy these leap years while you can, because they won’t last forever.

» READ MORE: This leap year will include a bonus ... a solar eclipse in April

The ancient Romans were renowned for their ingenuity, but the calendar wasn’t their strong suit, according to University of Houston classics scholar Richard Armstrong. In fact, before Julius Caesar gained power, it was “a terrible mess,” Armstrong said. The calendar originally was based on the moon, and over the course of the year it would grow multiple days out of whack with the solar cycle. Priests scrambled to keep the calendar somewhat in sync with the solar year, but in the tumultuous years before Caesar’s reign, they had other distractions. One result: Harvest festivals weren’t coinciding with actual harvests.

Caesar is credited with restoring order to the calendar. While Caesar had the authority, Armstrong said he is “sure” that most of the dirty work of calculation was done by astronomer Sosigenes of Alexandria. For starters, to get things straightened out, Caesar declared that the year 46 B.C. would be 445 days long. When order was restored and the great reset completed, Caesar imposed a 365-day calendar with a leap day every four years. He had it right, save for one detail.

To complete 574,395,530-mile solar orbit, it takes the Earth about 365.25 days. The emphasis is on about. According to NASA, that’s more precisely 365.24219 days. The upshot was that Caesar’s solution resulted in 11.23 unaccounted-for minutes a year. Not a big deal, right? Over a century, though, that comes to 18 hours and 42 minutes. And time flies when you’re hurtling through space at 67,000 mph. By the 16th century, the spring equinox had shifted from March 23 to March 11. Pope Gregory XIII made a critical adjustment, trimming the numbers of leap days by decreeing that they would be skipped in centuries that weren’t divisible by 4. That should keep working for most of us.

Currently, the calendar year is 365.2425 days, according to the U.S. Naval Observatory, and it would take 3,300 years before the calendar is off by a day. Sadly, however, nothing lasts forever, not even leap years. According NASA, the earth-moon interactions result in the lengthening of the day by about 1.4 milliseconds per century. Leap days eventually will be obsolete. It’s only going to take about four million years.

In the meantime, those anxiously awaiting spring can savor the illusion that the equinox will be arriving earlier than usual. It occurs at 11:06 p.m. on March 19, making it the earliest in 128 years. But it’s not as though the time interval from the winter solstice is any different, at just under 90 days. Winter is the briefest season in the Northern Hemisphere, three days shorter than spring, and four days fewer than summer. In its elliptical journey around the sun, the Earth makes its closest approach in January and speeds up a bit. It’s farther from the sun in summer. The heat and cold are mostly about the sun’s angle, not distance from the sun.

You may have noticed when entering your car in the afternoon that if it has been sitting in the sun, you don’t need to turn on the heater. The sun is rapidly gaining wattage this time of year. For snow to stick it has to be really cold, or falling at night, or at a very heavy rate. The record snowfall for Philly on a Feb. 29 is a whopping 1.0 inches. That is the lowest daily record amount for February and for the first 25 days of March.

» READ MORE: We again are running a snow deficit, and we won't make it up this February.

That record won’t be threatened this leap day.