How do I define a Date field  in the class to call in a Constructor

Here is my  class - 

public class CustomFields {
            public String fieldName;
            public String stringValue;
           
            public CustomFields(String fieldName, String stringValue){
                this.fieldName = fieldName;
                this.stringValue = stringValue;
            }

Here is the constructor 

jo.customFields = new List<CustomFields>();
            jo.customFields.add(new CustomFields('CX.LEADS360ID', currentOpp.Opportunity_ID__c));
            jo.customFields.add(new CustomFields('CX.LEADS360CAMPAIGN', currentOpp.Lead_Source_Name__r.Name));
            jo.customFields.add(new CustomFields('Date.CX.LEAD.CREATE.DATE', currentOpp.Legacy_Lead_Date_Added__c));
            jo.customFields.add(new CustomFields('CX.CRM.OWNER.EMAIL', currentOpp.Owner.Email));

I cannot add 

jo.customFields.add(new CustomFields('Date.CX.LEAD.CREATE.DATE', currentOpp.Legacy_Lead_Date_Added__c));

Because Opp.Legacy_Lead_Date_Added__c is a date field . How do I add a date variable in my class and call it in the constructor
       

Error I am getting 

Constructor not defined: [CustomFields].<Constructor>(String, Date)