I’m having a problem with dates. I have this code

        echo "<br>2a. Recall action date: ".$recallActionDate."<br>";
        $recallActionDate = date("Y-m-d H:i:s", strtotime($recallActionDate));
        echo "<br>2b. Recall action date: ".$recallActionDate."<br>";

this is a printout of the result:

2a. Recall action date: 26/06/2019

2b. Recall action date: 1970-01-01 00:00:00

I can’t figure out how the date is getting changed – any ideas please?