As reforming the computus was the primary motivation for the introduct... - dofaq.co
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As reforming the computus was the primary motivation for the introduct...

wikipedia - 17 Apr 2022
As reforming the computus was the primary motivation for the introduction of the Gregorian calendar in 1582, a corresponding computus methodology was introduced alongside the new calendar.[g] The general method of working was given by Clavius in the Six Canons (1582), and a full explanation followed in his Explicatio (1603).

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