      
      - returns: A length in (Julian) Days.
      */
-    func lengthOfSeason(_ season: Season, northernHemisphere: Bool) -> Day {
+    public func lengthOfSeason(_ season: Season, northernHemisphere: Bool) -> Day {
         let year = self.julianDay.date.year
         switch season {
         case .spring:

     
     - returns: A julian day of the TT time of the equinox.
     */
    func equinox(of equinoxType: EarthEquinoxType) -> JulianDay {
        let year = self.julianDay.date.year
        switch equinoxType {
        case .northwardSpring:

    ///   - planet: The considered planet. Cannot be the Earth.
    ///   - coordinates: The geographic coordinates for which to compute the twilights.
    /// - Returns: The rise, transit and set times, in Julian Day, and an error, if relevant.
    public func riseTransitSetTimes(for planetaryObject: KPCPlanetaryObject, geographicCoordinates: GeographicCoordinates) -> (riseTime: JulianDay?, transitTime: JulianDay?, setTime: JulianDay?, error: CelestialBodyTransitError?) {
        guard planetaryObject != .UNDEFINED else {
            return (riseTime: nil, transitTime: nil, setTime: nil, error: CelestialBodyTransitError.undefinedPlanetaryObject)
        }
