What kind of calendar system do people use in modern society?

The Gregorian calendar became the new calendar. Its introduction took place back in 1582 by the Pope himself. The basis for such a change was the shift of the day of the vernal equinox. Before that, the world used the Julian calendar, which was introduced during the time of Caesar. Nowadays, most countries use a new calendar, the so-called new style. The difference between the old and new calendar is 13 days.