Serializing a Timespan

So I am expanding on Roll a Ball and I was adding a high score system via a stopwatch and I found out that you can't serialize a timespan, directly at least. So I was wondering if there was a way around it. However, I could just have the code wrong. What happens is when I try to print the timespan after supposedly saving it, it just gives me 00:00:00.00. Here is the code.
My Save/Load function

 public void Load(){
         if (File.Exists (Application.persistentDataPath + "/ball.cid")) {
             BinaryFormatter bf = new BinaryFormatter ();
             FileStream file = File.Open (Application.persistentDataPath + "/ball.cid", FileMode.Open);
             Data col = (Data)bf.Deserialize (file);
             file.Close ();
             Colornum = col.Colornum;
             hs = col.hs;
             print ("Loaded");
         }
     }
     public void Save(){
         BinaryFormatter bf = new BinaryFormatter();
         FileStream file = File.Create (Application.persistentDataPath + "/ball.cid");
         Data col = new Data ();
         col.Colornum = Colornum;
         col.hs = hs;
         bf.Serialize (file, col);
         file.Close ();
         print ("Saved!");
     }
 
 }
 [Serializable]
 class Data{
     public int Colornum;
     public TimeSpan hs;
 }

My text function

 void Start () {
         string highScore = String.Format("{0:00}:{1:00}:{2:00}.{3:00}",
             SavingLoading.hi.hs.Hours, SavingLoading.hi.hs.Minutes, SavingLoading.hi.hs.Seconds,
             SavingLoading.hi.hs.Milliseconds / 10);
         score.text = highScore.ToString ();
         print (SavingLoading.hi.hs);
     }

My Other Text Function

 void Start () {
         SavingLoading.hi.mt = SavingLoading.hi.lvl1.Elapsed;
         string elapsedTime = String.Format("{0:00}:{1:00}:{2:00}.{3:00}",
             SavingLoading.hi.mt.Hours, SavingLoading.hi.mt.Minutes, SavingLoading.hi.mt.Seconds,
             SavingLoading.hi.mt.Milliseconds / 10);
         string highScore = String.Format("{0:00}:{1:00}:{2:00}.{3:00}",
             SavingLoading.hi.hs.Hours, SavingLoading.hi.hs.Minutes, SavingLoading.hi.hs.Seconds,
             SavingLoading.hi.hs.Milliseconds / 10);
         time.text = "You took: " + elapsedTime.ToString();
         hs.text = "Highs Score: " + highScore.ToString ();
         if (SavingLoading.hi.mt < SavingLoading.hi.hs) {
             SavingLoading.hi.hs = SavingLoading.hi.mt;
             print (highScore);
         }
         SavingLoading.hi.Save ();

Any help is appreciated! PS: If you need any other info, please tell me.