<Christopher Clavius>(https://dbpedia.org/resource/Christopher_Clavius) was a German Jesuit mathematician and astronomer who modified the proposal of the modern Gregorian calendar after the death of its primary author, <Aloysius Lilius>(https://dbpedia.org/resource/Aloysius_Lilius).|| Clavius would later write defences and an explanation of the reformed calendar, including an emphatic [ack.](acknowledgement) of Lilio's work.