First of all, if you were to Google “first day of spring,” you would find out it comes on March 20, but actually, for some people in the United States, it falls on March 19. This one fun fact makes this year the earliest that spring has arrived since 1896.
Added to that little bit of information is the fact that 2000 was a leap year, and that is unusual in itself because 1700, 1800, and 1900 were not leap years. How to explain the discrepancy? It is the fault of our imperfect Gregorian calendar system. Let’s check this out.
The vernal equinox is a celestial event
Even more exciting is the celestial event that will take place on March 20. This is the time of year when the Sun’s rays start crossing the Equator from the Southern to the Northern Hemisphere as our planet revolves around the Sun. This event is called an equinox, and there are two of them that occur every year. The first, occurring on March 20 or 21, is called the vernal equinox. The other, called the autumnal equinox falls on September 22 or 23.
Tomorrow’s vernal equinox is special because it marks a time when the Sun’s rays will shine directly on the Earth’s equator, a phenomenon where both sides of the Equator, the Southern, and Northern Hemispheres get an equal amount of light from the Sun. Think about that, it’s pretty cool.
Technically speaking, this means that in the Southern Hemisphere, autumn begins, while in the Northern Hemisphere, spring is starting. So why is this year’s first day of spring so early? It has everything to do with a term called the “tropical year,” the length of time that the Sun, as viewed from the Earth, takes to return to the same position along its ecliptic path. It is equivalent to exactly 365.24 mean solar days, or to be more precise, 365 days, 5 hours, 48 minutes, and 45 seconds.
The Gregorian calendar
The spring equinox will happen in the U.S. during the very early hours of Sunday (March 20) at 12:30 a.m. EDT and at 9:30 p.m. PDT March 19. To fully understand this, we have to look at the calendar we use today. Pope Gregory XII created the Gregorian calendar in 1582, and gave it 365 days, period. Well, except for every four years when the calendar had 366 days.
Pope Gregory XIII’s revision of the Julian calendar fixed the quarter-of-a-year discrepancy by making a rule, followed to this day. He stated that in addition to adding a day to the calendar every four years to account for the extra day, years ending in “00” should only be given leap years if they can be divided evenly by 400. So, as Tech Times says, “The March equinox was pushed approximately three-quarters early because 2000 was considered to be a leap year.”
