What ancient civilization is our current calendar most like?

Our current calendar is most similar to the ancient Roman calendar, specifically the Julian calendar introduced by Julius Caesar in 45 BCE. This calendar established a 365-day year with a leap year every four years, which laid the groundwork for the Gregorian calendar we use today. The structure of months and the concept of dividing the year into 12 months also have roots in earlier Roman practices. Additionally, the influence of the ancient Egyptians and their solar calendar further shaped our modern understanding of timekeeping.