On Halloween in 2020, a meme circulated on Facebook about purported features of Halloween 2020:
Alongside a post suggesting Halloween “2020 could be a little crazy,” a screenshot of a text-based status update meme read:
Next Halloween: On a Saturday,Full Moon & We set out clocks back that night. Halloween 2020 ain’t messing around.
October 31 2019 — also known as Halloween in many countries — fell on a Thursday, and typically fixed-date holidays such as Halloween, Christmas (December 25), and Valentine’s Day (February 14) fall on successive days each year. For example, Christmas was on a Tuesday in 2018, and a Wednesday in 2019.
By that logic, sharers might be inclined to deduce that since Halloween 2019 was on a Thursday, Halloween 2020 would naturally fall on a Friday. However, there’s just one catch: 2020 is a leap year.
Leap years occur once every four years, and during leap years, February has an additional day (February 29, or leap day.) The reason for that quirk of the calendar is to ensure that seasons stay static:
[As of 2019,] the last leap year was 2016, and the next one [would be] 2020! Leap days are extra days added to the calendar to help synchronize it with Earth’s orbit around the sun and the actual passing of the seasons. Why do we need them? Blame Earth’s orbit around the sun, which takes approximately 365.25 days. It’s that .25 that creates the need for a leap year every four years. During non-leap years, aka common years – like 2019 – the calendar doesn’t take into account the extra quarter of a day actually required by Earth to complete a single orbit around the sun. In essence, the calendar year, which is a human artifact, is faster than the actual solar year, or year as defined by our planet’s motion through space.
After February 29 2020’s irregular appearance, dated holidays shuffled forward by one day — kind of a bummer, as another Halloween on a Friday wouldn’t roll around until 2025:
- Halloween 2019, October 31, 2019: Thursday
- Halloween 2020, October 31, 2020: Saturday
- Halloween 2021, October 31, 2021: Sunday
- Halloween 2022, October 31, 2022: Monday
- Halloween 2023, October 31, 2023: Tuesday
- Halloween 2024, October 31, 2024: Thursday
- Halloween 2025, October 31, 2025: Friday
Valentine’s Day was not affected by the 2020 leap year until 2021 due to where it fell on the calendar, roughly two weeks before February 29 2020:
- Valentine’s Day 2019, February 14, 2019: Thursday
- Valentine’s Day 2020, February 14, 2020: Friday
- Valentine’s Day 2021, February 14, 2021: Sunday
- Valentine’s Day 2022, February 14, 2022: Monday
- Valentine’s Day 2023, February 14, 2023: Tuesday
- Valentine’s Day 2024, February 14, 2024: Wednesday
- Valentine’s Day 2025, February 14, 2025: Friday
Therefore, the first claim is accurate — Halloween would fall on a Saturday in 2020 despite falling on a Thursday in 2019, due to 2020’s status as a leap year.
A second claim was that Halloween 2020 fell on a full moon. According to Almanac.com, on October 13 2019 there was a full moon, the Full Hunter’s Moon; the subsequent full moon in 2019 (Full Beaver Moon) occurred on November 12.
In 2020, the Full Hunter’s Moon date was listed for both October 1 and October 31 (Halloween) 2020. A different resource noted that the second full moon in a single month was October 2020’s “blue moon.”
Space.com indicates there are actually two discrete definitions for a “blue moon”:
A “Blue Moon” is a fairly infrequent phenomenon involving the appearance of an additional full moon within a given period. But which period? It turns out there are two definitions of the term, and one was borne out of a misunderstanding of the other.
The older meaning defines a Blue Moon as the third full moon in a season that has four full moons. Called a seasonal Blue Moon, this occurs about every 2.5 years, according to NASA. More recently, the term Blue Moon has been applied to the second full moon within a single calendar month. There are roughly 29.5 days between full moons, making it unusual for two full moons to fit into a 30- or 31-day-long month. (This means that February will never have a Blue Moon.)
October 2020’s second full moon falls into the second category, when the term means “two full moons in a calendar month.” The former definition is indeed rarer, and according to NASA (using blue moon to mean “the second full moon in a calendar month”) in 2016, the rarer phenomenon of a “seasonal Blue Moon… only takes place about four times a century”:
[As of November 2016 the] last time this happened was in January and April of 1961 and it [would] not happen again until January and March of 2018. A double Blue Moon most commonly occurs in January/March but is also possible in January/April or January/May and only when there is no full moon at all in February. It is also possible to have a Blue Moon in December of one year and March of the next year, again, there is no full moon in the intervening February. See the links below for more details.
The meme’s second claim, that Halloween 2020 would fall on a full moon, is therefore true — and it was the less rare of the two types of blue moon.
Finally, the meme addressed one of two Daylight Saving Time (DST) adjustments slated for 2020. (Daylight Saving is the practice of setting clocks forward an hour from “standard time” during summer and back again in the fall, in order to make better use of natural daylight.)
In 2020, Daylight Saving Time would begin on March 8, when clocks would be skipped ahead one hour at 2 AM. Consequently, clocks would “fall back” an hour — often experienced as an extra hour in a day — on November 1 2020.
Although it looked like DST was not technically on Halloween 2020, the change would take place very early in the morning on November 1, and would for most people thus blend seamlessly into the night before. Since the clock’s changes would be most noted the following morning when people woke up the extra overnight hour, the confluence of DST and Halloween did mean that in essence people would receive one extra hour of sleep the next morning and could therefore celebrate for one extra hour the night before November 1 2020 — Halloween.
A meme that spread on Halloween 2019 claimed that Halloween 2020 fell on a Saturday during a full moon and coincided with Daylight Saving Time. All three of those things are essentially accurate, and at least two of the three might come as a surprise. The Halloween 2020 full moon is also a blue moon, the second of two full moons in October 2020. And due to a leap year, Halloween 2020 skipped falling on a Friday to fall on a Saturday.