The March Equinox at Saint Sulpice Church

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The March equinox, also known as the vernal or spring equinox in the Northern Hemisphere, occurred today. That’s the moment when the sun is directly in line with the equator; day and night are of about equal length.

For Earthlings, the March equinox means that spring has begin in the Northern Hemisphere and that autumn has begun in the Southern Hemisphere. For Christians following Western traditions and the Gregorian calendar, the March equinox is also related to Easter since Easter is celebrated on the first Sunday after the full moon occurring on or after the March equinox.

That’s why some churches, such as Saint Sulpice in Paris, have sundials of sorts specifically set to indicate the day of the equinox.

I was touring Saint Sulpice with a group of journalists today when at precisely 1 p.m. (i.e. noon Greenwich Mean Time), we gathered around the altar railing to watch the a spot of sun, coming from a hole in the window of the southern transept (above left in this photo), reach a marker in front of the altar.

(Saint Sulpice, you may recall, is the church that was fictionalized by Dan Brown in the “Da Vinci Code.”)

Saint Sulpice has transparent windows since narrative stained glass was passé when the church was built in the 17th century. The angle of that photo makes it appear that it was a bright out today, however it was in fact mostly cloudy in the early afternoon, with occasional bursts of sunlight. Despite the clouds we could make out the oval spot of sun moving across the marker.

The photo below was taken about two minutes after the magic moment. The spot of sun is that light rounded zone just above the marker. The line to either side of the marker is a meridian line.

Oddly enough there was no one else there to witness the passage of the equinox at this spot this year since. I can understand not being interested in a church, but aren’t people interested in the passage of time? Where was everyone? Upon leaving the church I could see that there are far more popular things to do in the Saint Sulpice quarter on a Saturday afternoon. One of them is to queue up for chocolates and/or pastries at the Pierre Hermé shop across the intersection.

To each his own use of his time.

Welcome to spring in the Northern Hemisphere.

– Text and photos GLK.


  1. Thank you for sharing this. I am reminded of the California missions having windows placed at a particular location to coincide with time of day when the sun could highlight a crucifix on the alter.


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