Ajax-Enabled WCF calls fail wit hDate Field

Hello,
I have the following class declaration 
[DataContract()] public class LeaveTimeRuleWCF : BaseWCF { [DataMember] public int UniqueId; [DataMember] public DateTime StartDate; } This class is used as paramter in my public WCF service method ; [OperationContract] public int Update(LeaveTimeRuleWCF a) { ...... }  
While calling the method I am getting the below shown error
 
Any idea hiow to fix this ?
 
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