Function To Check Adult in JavaScript

function checkIfAdult(idYear, idMonth, idDay, idColumnLabelToHighlight)
{
    var varYear = document.getElementById(idYear).value;
    var varMonth = document.getElementById(idMonth).value;
    var varDate = document.getElementById(idDay).value;

    var toDay = new Date();
    var AgeToCompare = new Date();
   
    AgeToCompare.setDate(varDate);
    AgeToCompare.setMonth((parseInt(varMonth)-1));
    AgeToCompare.setFullYear(varYear);
    //alert("Diff : ");
    var currentYear = toDay.getFullYear();
    var toCompareYear = AgeToCompare.getFullYear();
    //alert("Inside");
    var currentMonth = toDay.getMonth();
    var toCompareMonth = AgeToCompare.getMonth();
    //alert("Inside");

    var currentDay = toDay.getDate();
    var toCompareDay = AgeToCompare.getDate();
    //alert("Inside");
   
    var toReturn = true;
       
    //alert("Diff : " + (currentYear - toCompareYear)) ;
    document.getElementById(idColumnLabelToHighlight).style.color="#000000";   
    if( (currentYear - toCompareYear)  > 17 )   
    {
        //alert("> 17");
        toReturn = true;
    }
    else if( (currentYear - toCompareYear)  == 17 )   
    {
        //alert("= 17");
       //alert("Diff : " + (currentMonth - toCompareMonth)) ;
        if( (currentMonth - toCompareMonth)  > 0 )   
        {
            toReturn = true;
        }
        else if( (currentMonth - toCompareMonth)  == 0 )   
        {
            //alert("Diff : " + (currentDay - toCompareDay)) ;
            if( (currentDay - toCompareDay)  > 0 ) 
            { 
                toReturn = true;
            }   
            else
            {
                toReturn = false;
            }   
        }
        else
        {
             toReturn = false;
        }  
        document.getElementById(idColumnLabelToHighlight).style.color="#000000";
    }
    else
    {
        toReturn = false;
    }
    if(toReturn == false)
    {
        alert("Date Error : Only adults can book use this.");
        document.getElementById(idColumnLabelToHighlight).style.color="#ff0000";
        return false;
    }
    return toReturn;
}