JSFiddle - React, Tailwind, and code Playground

HTML

<input type="date" name="date" id="date_input" value="<?php echo $_GET['date']; ?>" class="date">


<a href="shopping_list.php?page_id=1&title=<?php echo $_GET['title']; ?>&date=" id="back_button">Back</a>

JavaScript

$("#date_input").on("change", function(){
  $("#back_button").attr("href", "shopping_list.php?page_id=1&title=<?php echo $_GET['title']; ?>&date="+this.value);
});