Residents of the Northeast are expecting a snowstorm this weekend, but they can warm themselves with one thought: It's spring. The new season officially arrives at 12:30am EDT on Sunday, March 20, notes the Old Farmer's Almanac. And as EarthSky points out, this happens to be the earliest arrival of spring since 1896—the result of a fluke in the calendar. "In a nutshell, this earliest spring is happening because the tropical year, as measured between successive March equinoxes, doesn't have an even number of days (365.242 days)," explains the post. And so leap years (366 days) vs. non-leap years (365 days) adjust its timing.
And Pope Gregory XIII threw a wrench into things: In 1582 he decreed that leap year not fall on centennial years, unless that year was divisible by four—so 2000 was considered a leap year, but not 1900. That "causes the March equinox to arrive roughly three-quarters of a day earlier in the 21st century than at corresponding years in the 20th century," explains the post. Every four years, the March equinox will shift earlier, ultimately bringing us to the earliest one of the 21st century: 10:03am March 19, 2096. Come 2100, where there is also no leap year, the March equinox times will be pushed forward, and will once again occur on March 21 in 2102. As for that potential nor'easter, it looks like Sunday will be the day for snow, but much remains iffy about the forecast, reports Weather.com.