Convert Timer to HH:MM:SS

How do I convert my GUI timer into HH:MM:SS

This is my bomb script

var PlantTime = 5.0;
var InSite = false;
var Planting = false;

var Plant = 0;
var BombGO : GameObject;


static var DonePlant = false;

function Start(){
BombGO.SetActiveRecursively(false);
}

function Update (){
if(InSite == true){
if(Input.GetKeyDown("f")){
isPlanting();
}
}
if(Plant == 1){
PlantTime -= Time.deltaTime;
}
if(PlantTime <= 0){
PlantTime = 0;
BombGO.SetActiveRecursively(true);
InSite = false;
Planting = false;
DonePlant = true;
}
if(TruckAnim.IsDone == true){
BombGO.SetActiveRecursively(false);
}
}

function isPlanting(){
Planting = true;
Plant = 1;
}

function OnGUI(){
if(InSite == true){
if(Planting == false){
GUI.Label(new Rect(Screen.width / 2 - 25, Screen.height / 2 + 25, 150, 30), "Press 'F' to plant a bomb.");
}
}
if(Planting == true){
GUI.Label(new Rect(Screen.width / 2, Screen.height / 2, 150, 20), "Plant Time: " +PlantTime);
}
}

function OnTriggerEnter (other : Collider){
if (other.gameObject.tag == "Player") {
InSite = true;
}
}

Instead of my timer being 3.815446 I just want it to display 3, for example
How could I do this please help.

Here’s a simple example of a game timer showing in format HH:mm:ss. There are many ways to do this, this is how I prefer. You will obviously need to modify this to your liking.

using UnityEngine;
using System.Collections;

public class TimerExample : MonoBehaviour 
{
	string s;
	
	void Update()
	{
		s = System.TimeSpan.FromSeconds((int)Time.timeSinceLevelLoad).ToString();
	}
	
	void OnGUI()
	{
		GUILayout.Label(s);
	}
}