FRONTEND_MVC/modules/control/views/layouts/footer.php

<footer class="main-footer">
    <strong>Copyright &copy; 1999-<?=date("Y")?></strong>
    <div class="float-right d-none d-sm-inline-block">
        <b>Version</b>  <?=\Yii::getVersion();?>: <?=round((REV-strtotime("2021-01-01"))/86400,2);?>
    </div>
</footer>