How to make a short winter day?

Question

C++ / C#

There is a directional light and a script for it:

void Start () {

        latitude = degrees + ((double)minutes / 60) + ((double)seconds / 3600);
        inclination = 23.5 * Mathf.Sin((360 * (currentDay - 81)) / 365);
        solarAzimut = latitude - 23.5 - inclination;

        transform.rotation = Quaternion.Euler(360-(float)solarAzimut, 180, 0);
    }
  
  void Update () {
        transform.Rotate(Vector3.up, DayLength * Time.fixedDeltaTime);
  }

The script describes the change in the position of the Sun during the seasons.
The problem is that the length of the day and night are always equal to each other.
How can I change the directional light?
An illustration of what I want to do

Answer 1

That's it, I understand.
It is necessary to make the movement of the sun along an elliptical trajectory