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Spring Equinox

Why Easter is the Same Time Every Year Just on a Different Date

What the Alignment of the Sun and the Moon Tell Us About Easter

Did you know there is a three-part calculation to determine the date of Easter? The first part of the calculation happened today?

Step One – Light over Darkness

In 2017, March 20th is the first day of Spring. It started at 6:28 a.m. EDT to be precise. So how is that determined? Well, look to the sky for that answer. No, God will not call out to you in a sunshiny voice “Hey you, smile, it’s Spring”. Spring is actually determined in the Northern Hemisphere when we experience the Vernal Equinox*, that time when the sun crosses the celestial equator making its way northward. For a moment, all around the world, daylight and nighttime hours are nearly equal.

As a practical matter, it means that people in the Northern Hemisphere will gradually begin to experience longer days and shorter nights. This leads to warmer days, earlier dawns and later sunsets.

So what does this have to do with Easter? It is step one of the calculation to determine the date: When the daylight becomes greater than darkness.

the full moon

Step Two – The Light of the Night Sky

The second element in determining the date of Easter is found in the night sky. Step outside and look at the moon. We are looking for the full moon. At this time, it is getting less visible since we experienced a full moon back on March 12th. This means we will need to wait until April 11th for the next full moon. So what does the full moon have to do with anything related to Easter?

Remember the first part of the formula; Daylight begins to reign over night? Now we have the brightest light of night shining in the darkness. So what is next?

Step Three – the Lord’s Day

Every Sunday we celebrate the Lord’s resurrection. From this point on we look to the calendar, not the sky. We simply check the calendar to find the next Sunday, because that Sunday is Easter. For us, this year, the date is April 16th, with the Vigil beginning at sundown on the 15th.

So, Easter is the First Sunday, after the first full moon, after the Spring Equinox. It is the same time every year, just on a different date.


*Etymology of Equinox: The word Equinox comes from Latin, where words aeuus (equal), and nox (night), come together to mean “equal night”.

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