function setHidden(prefix,syear){
        var field_day = document.getElementById(prefix+"_day");
        syear=syear-1;
        var field_month = document.getElementById(prefix+"_month");
        var field_year = document.getElementById(prefix+"_year");
        var field_min = document.getElementById(prefix+"_min");
        var field_hour = document.getElementById(prefix+"_hour");

		var stext= document.getElementById(prefix);
		if( 
			field_day.selectedIndex == 0 || 
			field_month.selectedIndex == 0 || 
			field_year.selectedIndex == 0 || 
			( field_min && field_min.selectedIndex == 0 ) || 
			( field_hour && field_hour.selectedIndex == 0 ) 
		) {
			stext.value = "";
			return;
		}
		
        stext.value="";
		if(field_day.selectedIndex<10)
			stext.value+="0";
		stext.value+=field_day.selectedIndex+".";
		if(field_month.selectedIndex<10)
			stext.value+="0";
		stext.value+=field_month.selectedIndex+".";
		stext.value+=(field_year.selectedIndex+syear)+" ";
        if(field_hour){
            if(field_hour.selectedIndex==24)
                stext.value+="00";
            else if(field_hour.selectedIndex<10)
                stext.value+="0"+field_hour.selectedIndex;
            else
                stext.value+=field_hour.selectedIndex;
        }
        if(field_min){
    		if(field_min.selectedIndex==60)
	    		stext.value+=":00";
		    else if(field_min.selectedIndex<10)
			    stext.value+=":0"+field_min.selectedIndex;
		    else
			    stext.value+=":0"+field_min.selectedIndex;
        }
}