Easter is a big deal for Christians, and there is a good reason for that: Easter celebrates the resurrection of Jesus Christ, the one who died for us. But have you ever wondered why the date of Easter changes every year? It’s a function of the lunar calendar and the solar calendar when it comes to calculating this.
Here are valid reasons Easter changes yearly, but Christmas doesn’t:
The Date of Easter Is a Function of Both the Lunar and Solar Calendars.
To explain the first part of the introduction sentence, you need to know that Easter is always celebrated on the first Sunday after the first full moon after the Spring Equinox (March 21). That date can vary from year to year—and as we’ll see in a moment, it has a lot to do with how different calendars work.
The reason it keeps changing is that not all calendars are made equal. One is based on the moon’s phases (the lunar calendar), and one is based on the sun’s movement through space (the solar calendar). Even though March 21 marks two important dates in our calendar year (the spring equinox and Passover), those two events won’t necessarily fall on the same day in any given year—and therefore, neither will Easter.
Christmas, on The Other Hand, Is Fixed to The Solar Calendar.
Christmas and Easter are celebrated on different days, but they’re still a part of the same holiday.
Christmas is on December 25 yearly because it’s fixed to the solar calendar. The solar calendar is based on the position of the Earth with the sun, so it always stays the same. Easter, on the other hand, changes from year to year because it’s based on a lunar calendar. A lunar calendar is determined by how many days there are between full moons (a full moon is when we see all of Earth’s natural satellites in their entirety).
Easter can fall anywhere between March 22 and April 25 each year!
The Chinese Calendar Fixes Both Lunar and Solar Movements.
Consequently, Chinese New Year (also known as Spring Festival) is fixed with the solar year, but it’s also fixed to the lunar month. If you want to celebrate Chinese New Year at the same time every year, you’d have to do some complicated math based on both the solar and lunar cycles.
It is impossible for most people because they don’t know how to do such complex calculations. Instead, they use a calendar that fixes the holiday to a specific day of the year—in this case, January 23—so that everyone can celebrate it on their terms and on a relatively regular basis.
Two Different Calendars Determine the Date of Easter.
The first is the Gregorian calendar, which we use today. It was created in 1582 by Pope Gregory XIII and is based on a solar year (365 days) and a leap year every four years. This calendar has been in use for over 400 years and determines the majority of holidays in our society today.
The second is the Julian calendar, which Julius Caesar created in 45 BC, and it was based on an actual solar year—365.25 days—and a leap year every four years. Most of Europe used the Julian calendar until 1582, when Pope Gregory XIII decided to replace it with his calendar, which was based on a real solar year (365 days).
So why does Easter change every year, but Christmas doesn’t? Because two different calendars determine its date!
Passover falls on a full moon because it’s celebrated on the 14th day of Nissan – so Easter falls on a full moon too.
Easter falls on a full moon because it’s celebrated on the first Sunday after the first full moon following the spring equinox, which is always on March 21. Passover falls on a full moon because it’s celebrated on the 14th day of Nissan – so Easter falls on a full moon too.
If you have any questions about why Easter changes every year, but Christmas doesn’t, please send them over! We’re happy to help you understand the difference between the two holidays and how they relate.