Can you help me to solve the issue and understand it better as I am new to Coding world. 

I know the issue is because the Apex Class Method's Access modifier **"Private"** causing the trouble, as I am not able to access it from from Test Methods in Test class 

**Apex Class [Method DateWithin30Days is Private]**

    public class verifyDate{

    	public static Date CheckDates(Date date1, Date date2){
    	if(DateWithin30Days(date1,date2))
    		return date2;
        else
    		return SetEndOfMonthDate(date1);
    	}
    	
    	private static Boolean DateWithin30Days(Date date1, Date date2){ //Private
    	Date date30Days = date1.addDays(30); 
    	if( date2 > date30Days) 
            return false; 
    	else 
            return true; 
    	} 
    }


**Test Class [Test method - verifyDate.DateWithin30Days(dt1, dt2) throwing error]** 
>  Error Method is not visible: verifyDate.DateWithin30Days(Date, Date)


    @IsTest
    public class TestVerifyDate {   
        @IsTest 
        static void checkDatesTest(){
            Date Dt1 = Date.today();
            Date Dt2 = Date.today()+20;
            Date Dt = verifyDate.CheckDates(Dt1, Dt2);
            system.assertEquals(Dt2, Dt);
            Dt2      = Date.today()+40;
                   
            Dt = verifyDate.CheckDates(Dt1, Dt2);
            system.assertEquals(Dt1.addMonths(1).toStartofMonth().addDays(-1),Dt);
        }
        
        @IsTest 
        static void DateWithin30DaysTest(){
            Date Dt1 = Date.today()+40;
            Date Dt2 = Date.today();
            Boolean Flip1 = verifyDate.DateWithin30Days(dt1, dt2);//Error
            system.assertEquals(False, Flip1);
            
            Dt1 = Date.today();
            Dt2 = Date.today()+90;
            Boolean Flip2 = verifyDate.DateWithin30Days(dt1, dt2);//Error
            system.assertEquals(False, Flip2);        
        }
    }


can you help me to understand, how can I access the Private Apex Class method DateWithin30Days from Test Class Method DateWithin30DaysTest(). Please let me know what modification I need to do in Test Class method to achieve this?