Automatically update year in email footer

I’m trying to include a copyright and a year at the bottom of my emails that I’m hoping will automatically update yearly. Is there any code I can use to make that happen? I’ve tried the one I use on my website:
<?php echo date("Y"); ?>

Plus these:
<?= date("Y") ?>

<span id="year"></span></p>

  <script>
  document.getElementById("year").innerHTML = new Date().getFullYear();
  </script>

But none of them work.

Thanks for your help!