Help, getting ambiguous reference error

using "using System;" causes error

"Object is an ambiguous reference between Unity.Object and object"

for spriteArray

I need to use "using System;" for "TimeSpan" and "DateTime" calculations

e.g.

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 using System;
 
 public class arrayAndDateTimeTest : MonoBehaviour 
 {
     
     public Object [] spriteArray;
     private DateTime myDateTime;
     private TimeSpan myTimeSpan;
 
     // Use this for initialization
     void Start () 
     {
         spriteArray = Resources.LoadAll ("EnergyBarSprites/Energy Bars"); //EnergyBarSprites
         myDateTime = System.DateTime.Now;
         myTimeSpan = TimeSpan.FromMinutes(10);
     }
 }