The event marking the beginning of a new year in the Gregorian calendar is New Year's Day, celebrated on January 1st each year. The Gregorian calendar, which is the calendar system most widely used today, was introduced by Pope Gregory XIII in 1582, reforming the Julian calendar to better align with the solar year. New Year's Day is recognized globally and is celebrated with various customs and traditions, such as fireworks, parties, and resolutions for self-improvement. The transition to a new year symbolizes fresh beginnings and opportunities for personal growth and reflection, making it a significant event in numerous cultures around the world.