function validarDatas(di, df){

    if(di == "" && df == "")
        return true;

    if( !validarData(di) || !validarData(df))
        return false;

    var separaData = di.split('/'); // 01/01/2012
    var dataInvertidaInicial = separaData[2]+separaData[1]+separaData[0]; // 20120101

    var separaDataFinal = df.split('/'); // 10/01/2012
    var dataInvertidaFinal = separaDataFinal[2]+separaDataFinal[1]+separaDataFinal[0]; // 20120110
    if(di != null && di != ""){

        if(dataInvertidaInicial > dataInvertidaFinal){
            alert('A data final e menor que a data inicial');
            return false;
        }

        return true;
    }

    return false;
}
function validarData(data){
      return /^((([0][1-9]|[12][0-9])\/02\/(19|20)([13579][26]|[02468][048]))|(([0][1-9]|[1][0-9]|[2][0-8])\/02\/(19|20)([02468][12356]|[013579][13579]))|((([0][1-9]|[12][0-9]|30)\/(0[469]|11)|([0][1-9]|[12][0-9]|3[01])\/(0[13578]|1[02]))\/(19|20)[0-9][0-9]))$/.test(data);
    }