section_path: Astronomical years/Variation in the length of the year and the day
section_name: Variation in the length of the year and the day
paragraph_text: Variation in the length of the year and the day
  
  The exact length of an astronomical year changes over time.
  
  Numerical value of year variation Mean year lengths in this section are calculated for 2000, and differences in year lengths, compared to 2000, are given for past and future years. In the tables a day is 86,400 SI seconds long.