section_path: Intercalation/Gregorian calendar
section_name: Gregorian calendar
paragraph_text: Gregorian calendar
  
  The Gregorian calendar aims to ensure that the northward equinox falls on or shortly before March 21 and hence it follows the northward equinox year, or tropical year. Because 97 out of 400 years are leap years, the mean length of the Gregorian calendar year is 365.242 5 days; with a relative error below one ppm (8·10) relative to the current length of the mean tropical year (365.242 189 days) and even closer to the current March equinox year of 365.242 374 days that it aims to match.