The desired ecliptic longitude of date in degrees. This may be any value in the range [0, 360), although certain values have conventional meanings:
When `targetLon` is 0, finds the March equinox,
which is the moment spring begins in the northern hemisphere
and the beginning of autumn in the southern hemisphere.
When `targetLon` is 180, finds the September equinox,
which is the moment autumn begins in the northern hemisphere and
spring begins in the southern hemisphere.
When `targetLon` is 90, finds the northern solstice, which is the
moment summer begins in the northern hemisphere and winter
begins in the southern hemisphere.
When `targetLon` is 270, finds the southern solstice, which is the
moment winter begins in the northern hemisphere and summer
begins in the southern hemisphere.
A date and time known to be earlier than the desired longitude event.
A floating point number of days, which when added to dateStart,
yields a date and time known to be after the desired longitude event.
The date and time when the Sun reaches the apparent ecliptic longitude targetLon
within the range of times specified by dateStart and limitDays.
If the Sun does not reach the target longitude within the specified time range, or the
time range is excessively wide, the return value is null.
To avoid a null return value, the caller must pick a time window around
the event that is within a few days but not so small that the event might fall outside the window.
Searches for when the Sun reaches a given ecliptic longitude.
Searches for the moment in time when the center of the Sun reaches a given apparent ecliptic longitude, as seen from the center of the Earth, within a given range of dates. This function can be used to determine equinoxes and solstices. However, it is usually more convenient and efficient to call Seasons to calculate equinoxes and solstices for a given calendar year.
SearchSunLongitudeis more general in that it allows searching for arbitrary longitude values.