Day/Night Cycle in Unity (Quick Version)

DayNightController.cs

using UnityEngine;

public class DayNightController : MonoBehaviour
{

    // The main light source reference from the scene
    [SerializeField]
    private Light sun;

    // This sets the length of a full day cycle in seconds. Here, it's set to 60 seconds by default. You can adjust this for you need.
    [SerializeField]
    private float dayDuration = 60.0f;

    // This is the color of the light at day time
    [SerializeField]
    private Color dayColor = Color.white;

    // This is the color of the light at night time
    [SerializeField]
    private Color nightColor = new Color(0.1f, 0.1f, 0.3f);

    // This represents the current time of day as a value between 0 and 1. We split the time of day as four parts (0.25 - dawn, 0.5 - nooon, 0.75 - evening, 1 - night)
    // 0.25 is used as the starting value to begin the cycle at dawn.
    private float timeOfDay = 0.25f;

    
    void Update()
    {
        // Increase the timeOfDay
        timeOfDay += Time.deltaTime / dayDuration;

        // If timeOfDay reaches 1, we need to set it to 0 for continuous cycle of day/night.
        if (timeOfDay >= 1f) timeOfDay -= 1f;

        // This rotates the sun based on the time of day.
        // timeOfDay * 360f converts the 0-1 range to 0-360 degrees. The -90 offset starts the sun at the horizon at dawn.
        // 170 on the Y-axis tilts the sun's path to create more realistic lighting angles.
        sun.transform.rotation = Quaternion.Euler((timeOfDay * 360f) - 90, 170, 0);

        // This sets the color of the directional light representing the sun.
        // We use Color.Lerp, linear interpolation function to blend between day and night.
        // This is the key to creating a smooth back-and-forth transition.
        // Mathf.PingPong creates a value that ping-pongs back and forth between 0 and the second parameter (1 in this case).
        // timeOfDay * 2 is used because we want a full cycle (night to day to night) to occur over the course of a single day.
        
        /*
         * Here's how it works over time:
         *   When timeOfDay is 0, PingPong returns 0, so the color is nightColor.
         *   As timeOfDay increases to 0.25, PingPong approaches 0.5, blending to a middle color.
         *   At timeOfDay 0.5, PingPong returns 1, so the color is fully dayColor.
         *   As timeOfDay continues to 0.75, PingPong goes back to 0.5, returning to the middle color.
         *   When timeOfDay reaches 1, we're back to nightColor.
         * This creates a smooth cycle: night → dawn → day → dusk → night, all using a single line of code.
        */
        sun.color = Color.Lerp(nightColor, dayColor, Mathf.PingPong(timeOfDay * 2, 1));

    }
}