Day/Night Skybox

I have modified a script I found, my problem with the script is that the Blend doesn't apply probably even though the value is right, its like the Material.SetFloat("_Blend", Blend) Doesn't run:

 #pragma strict
     
 var TOD : float;
 public var sun : GameObject;
 var NightAmbientLight : Color;
 var DuskAmbientLight : Color;
 var MorningAmbientLight : Color;
 var MiddayAmbientLight : Color;
 var SunNight : Color;
 var SunDay : Color;
 
 var NightSkyBox : Material;
 var DaySkyBox : Material;
 var NightBlendSkybox : Material;
 var DayBlendSkybox : Material;
 
 private var skybox : Skybox;
 
 // Use this for initialization
 function Start() {
     skybox = GetComponent(Skybox);
     sun = GameObject.Instantiate(sun, Vector3.zero, Quaternion.identity);
 }
 
 var DayLength = 24.0f;
 var Hour = 0.0f;
 
 var Blend : float;
 
 function Update() {
     Hour = Mathf.Clamp(Hour, 0, 1) == 1 ? 0 : Hour;
     Hour += (Time.deltaTime / DayLength) / 60;
     
     TOD = Hour * 24;
     Blend = (Hour % (1.0f / 12.0f)) * 12.0f;
     
     sun.GetComponent(Light).transform.localEulerAngles = new Vector3((Hour * 360) - 90, 0,0);
     sun.GetComponent(Light).color = Color.Lerp(SunNight, SunDay, Hour);
         
     if (TOD > 4 && TOD < 6) {
         skybox.material = NightBlendSkybox;
         skybox.material.SetFloat("_Blend", Blend);
         RenderSettings.ambientLight = Color.Lerp(NightAmbientLight, MorningAmbientLight, Blend);
         //it is Morning
     } else if (TOD > 6 && TOD < 8) {
         skybox.material = DaySkyBox;
         skybox.material.SetFloat("_Blend", Blend);
         RenderSettings.ambientLight = Color.Lerp(MorningAmbientLight, MiddayAmbientLight, Blend);
         //it is Day
     } else if (TOD > 18 && TOD < 20) {
         skybox.material = DayBlendSkybox;
         skybox.material.SetFloat("_Blend", Blend);
         RenderSettings.ambientLight = Color.Lerp(MiddayAmbientLight, DuskAmbientLight, Blend);
            //it is Dusk
     } else if (TOD > 20 && TOD < 22) {
         skybox.material = NightSkyBox;
         skybox.material.SetFloat("_Blend", Blend);
         RenderSettings.ambientLight = Color.Lerp(DuskAmbientLight, NightAmbientLight, Blend);
         //it is Night
     }
 }