In the folklore of Scandinavia, Tycho Brahe days (Danish: Tycho Brahes-dage; Norwegian: Tycho Brahedager; Swedish: Tycho Brahe-dagar) are days judged to be especially unlucky, especially for magical work, and important business transactions (and personal events). Tycho Brahe (1546–1601) was a Danish astronomer, astrologer, and alchemist and as such achieved some acclaim in popular folklore as a sage and magician.
The idea that certain calendar dates are lucky or unlucky is of ancient origin, going back as far as the Mesopotamian civilizations. Tables that identify lucky and unlucky days are sometimes known by their German category name Tagwählerei.
The received idea concerning the origin of Tycho Brahe days was that
In his travelogue A Poet's Bazaar, Hans Christian Andersen alludes to Tycho Brahe's death while living in exile, in Prague, observing that
However, no mention of the days now called Tycho Brahe days is actually found in any work of Tycho Brahe. They nevertheless are often referenced in almanacs and recur in Scandinavian folklore. In the Cyprianus tradition, Tycho Brahe days are considered unlucky for magical work; several of the spells in the Black Books of Elverum note that they should not be carried out on a Tycho Brahe day.
These days were supposed to be unlucky to perform tasks such as getting married, starting a journey, or to fall ill on. Some versions claim that Tycho Brahe also identified several days as particularly lucky:
Some lists omit certain days, or add others; there is no standard list. Denmark was on the Julian calendar until 1700, when it switched to the Gregorian calendar.
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