var fromDate = new Date();
var now = new Date();

function disallowDatesFrom(date) {
   if( date.getYear() < now.getYear() ||
       date.getYear() == now.getYear() && date.getMonth() < now.getMonth() ||
       date.getYear() == now.getYear() && date.getMonth() == now.getMonth() && date.getDate() < now.getDate())
        return true;
    return false;
}


function disallowDatesTo(date) {
    fromDate = new Date( 
            document.getElementById( txtDepDateFrom ).value.substr( 6 ),
            document.getElementById( txtDepDateFrom ).value.substr( 3, 2 ) - 1,
            document.getElementById( txtDepDateFrom ).value.substr( 0, 2 ) 
    );
        
    if( date.getYear() < fromDate.getYear() ||
        date.getYear() == fromDate.getYear() && date.getMonth() < fromDate.getMonth() ||
        date.getYear() == fromDate.getYear() && date.getMonth() == fromDate.getMonth() && date.getDate() < fromDate.getDate() )
        return true;
          
    return false;
}