What are the ‘Perilous Days’ of the Year?

 Are you wondering which days it might be best not to get out of bed? In the Middle Ages they wondered that as well, and made use of astrology and signs from the heavens to help them figure this out. A helpful writer from the 15th century even made a list of ‘Perilous Days’

Irene Meekes – van Toer explains that the idea of Perilous Days was widespread in the Middle Ages:


At the root of the idea appears to lie the conviction that unfortunate events are apt to repeat themselves on particular days.  So, for instance, in ancient Rome the Ides of March (March 15th) was considered an unlucky day after the assassination of Julius Caesar. In the Middle Ages, the notion was embraced that all the calamitous affairs in the Bible (such as Cain’s murder of Abel, the deluge, John the Baptist’s decapitation and of course the crucifixion of Christ) had taken place on Fridays. Friday therefore was felt to be a particularly dark day. Mondays were also considered unsuitable by some. However, most unlucky days were not confined to any specific day of the week.

Van Toer researched a later 15th century manuscript that contained an astrological calendar, and found that the author made his own list of what he titled Perilous Days:


The best and wisest scholars have named forty-five bad and unhealthy days. Anyone born on any of these days will not live long. And should anyone get ill, he will die; and should anyone travel abroad, his return is a matter of chance. If a man has intercourse with a woman or a woman with a man, they will have to separate due to poverty. And should anyone begin any great thing on any of these days, it will not come to a good end.

Although he says there are 45 perilous days, the author then goes on to list these only 38 days:

January 1st, 2nd, 4th, 9th, 19th, 25th

February 4th, 18th, 27th

March 1st, 3rd, 16th, 18th

April 10th, 12th, 20th

May 3rd, 15th, 16th, 20th

June 4th, 10th, 16th

July 12th, 13th, 19th

August 1st, 20th, 30th

September 3rd, 17th, 21st

October 3rd, 6th, 22nd

November 2nd, 5th, 17th, 18th

The entire month of December was left out in the manuscript, leaving us unable to warn you which of those days to be wary of!

The author also tell us about a few good days, including the “Days Conferring Incorruptibility”. He explains:


There are three days in the year when anyone is born on any of those days, he cannot rot before doomsday. That is the first of February, the last of April and the first of August.

You can read the full text of this work in Als die maen is inden weder: Practical Advice in a Late-Fifteenth-Century Astrological Calendar Manuscript – Amsterdam UB MS XXIII A 8, a Master’s thesis by Irene Meekes – van Toer from Utrecht University

Top Image: Sinking ships – British Library MS Additional 10292 f. 36v