Inter gravissimas was a papal bull issued by Pope Gregory XIII on 24 February 1582. The document, written in Latin, reformed the Julian calendar. The reform has conventionally come to be regarded as a new calendar in its own right, called the Gregorian calendar, named after Pope Gregory XIII. In the realm of orthodox christendom whose liturgical cycles did not apply the Inter gravissimas, the reformed calendar is noted as the New Style. The reformed Julian Calendar is used in most countries today, relatively independent of religious orientation of its populaces.