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The Gregorian Calendar's main architect was the Jesuit mathematician Christopher Clavius, link below:-
Christopher Clavius - Wikipedia, the free encyclopedia
On the Prime Meridian and every 15 degrees of longitude there after, the Gregorian Calendar points to to Sirius in the middle of the sky at midnight on 1st January, slightly modified from the ancient Egyptian Calendar where Sirius rose with the Sun on New Years Day, the change was made by the invention of the clock!
Sirius midnight culmination New Year’s Eve | Tonight | EarthSky