How to insert custom code into a sidebar (Php included)

Hi there, I have this code to add something like a timer / countdown specify to a site :

<script type="text/javascript">
    //Variables
    var epoch_time = <?= time() ?>000;
    var startHour = 19;
    var finalHour = 3;

    //Funcion principal
    function timer_test() {
        var date1 = new Date(epoch_time);
        var seconds = date1.getSeconds();
        var minutes = date1.getMinutes();
        var hours = date1.getHours();
        var diferencehours = startHour - hours -1;
        var diferenceminutes = 60 - minutes -1;
        var diferenceseconds = 60 - seconds;

        if (hours >= startHour || hours < finalHour) {
            $("#timer").html("All of our services are running.");
        }
        else if(hours < startHour && hours >= finalHour) {
            $("#timer").html(diferencehours + ":" + diferenceminutes + ":" + diferenceseconds);
        }

        epoch_time += 1000;
    }

    $(function() {
        //Interval
        setInterval(timer_test,1000);
    });

  </script>

And I have a DIV called timer, where I will post the timer.

So, how do I include this script? Adding full script + id to a text widget into a sidebar doesn’t work (Exclude php code it seems)

Thanks