We currently use the Gregorian calendar as the internationally accepted civil calendar. It was introduced in 1582 by Pope Gregory XIII to replace the Julian calendar and better align the calendar year with the Earth's solar year. The Gregorian calendar has 12 months of varying lengths, with a common year of 365 days and a leap year of 366 days every four years, except for years divisible by 100 but not by 400

. This calendar is the global standard for civil purposes and is used by most countries worldwide, including for business and everyday dates. It is also the basis for the international ISO 8601 date and time standard

. While the Gregorian calendar is predominant, other calendars like the Islamic, Hebrew, Hindu, Chinese, and Persian calendars are still used for religious and cultural purposes in various regions