Jamie Carter observes how dependent religious events such as Easter are on the moon. Humans celebrate these events not because of a numbered calendar date, but because of lunar cycles.

When is Easter? That’s easy—Easter is on Sunday, April 12, 2020 for western christians and on Sunday, April 19, 2020 for eastern orthodox christians.

Two dates, forever changing—Easter does not have a specific date.

Unlike Christmas Day, it changes every year depending on something that most people don’t often associate with the christian religion—the moon.

For the world’s 1.8 billion muslims, the exact date of Ramadan is determined by the lunar cycle—with the physical sighting of the crescent moon the day after a New Moon the critical factor. In 2020, that’s Thursday, 23 April—the evening after the next New Moon—unless the crescent isn’t sighted, in which case it will begin the evening after when the New Moon is higher in the post-sunset sky…

Easter is celebrated by roman catholics and protestant christians on the first Sunday after the first full moon occurring on or after the vernal equinox as determined by the Gregorian calendar. That’s the rule. Since the equinox occurred on March 20, 2020 and the “Super Pink Moon” appeared on April 7, 2020, so the date of Easter Sunday was automatically set for Sunday, April 12, 2020. It’s been that way since the year 325 A.D…

Although its 99% a lunar festival in terms of the date it’s held, Easter isn’t just determined by the moon’s phases. The ecclesiastical authorities fix the vernal equinox at March 21, thereby limiting the dates when Easter can occur…

Clocks are a modern invention, as is the convention of global calendars standard time. “Prior to the Gregorian calendar, which is our standard calendar now, calendars were set by the phases of the moon because we didn’t have clocks,” said Dr. Jackie Faherty, Senior Scientist and Senior Education Manager jointly in the Department of Astrophysics and the Department of Education at the American Museum of Natural History.

The Gregorian calendar is a solar calendar that evolved from a lunar calendar. “Standards of time only began when people wanted to set train timetables, and this idea that we have a universal time that we can all get from looking at our watch is something we take for granted,” said Faherty…

Much of our calendar comes from astronomy,” said Faherty, stating that Monday is named after the Moon. “It’s a constant and observable feature that you can get your own understanding of, with its changing phases a great way of tracking the seasons.”

Our concepts of time, and the language we use to talk about it, owe a lot to the Moon and the Sun.“There’s so much to our keeping track of our time that’s related to astronomy, and so much in the early days was set and understood by the Moon—so that was the way that many religious calendars were calculated, and still are today,” said Faherty.

Carter, J. 2020. ‘When Is Easter? The Lunar Festival That’s Determined By The Movements Of The Moon.’ Forbes. April 9, 2020. https://www.forbes.com/sites/jamiecartereurope/2020/04/09/when-is-easter-the-lunar-festival-thats-all-about-the-movements-of-the-moon/#4c8acf3316d7