section_path: Years/Vernal Equinox
section_name: Vernal Equinox
paragraph_text: Vernal Equinox
  
  The first day of each year (Naw-Rúz) is the day (from sunset to sunset) in Tehran containing the moment of the vernal equinox. This is determined in advance by astronomical computations from reliable sources.
  
  Since the Gregorian calendar is not tied to the equinox, the Gregorian calendar shifts around by a day or two each year, as shown in the following table.