If you show registration date in Author page, Use this code in author.php
<?php global $wp_query; $registered = date_i18n( "M m, Y", strtotime( get_the_author_meta( 'user_registered', $wp_query->queried_object_id ) ) ); echo 'Member since ' . $registered; ?>
If you show registration date in Single post, Use this code in single.php
<?php $user_ID = $post->post_author; $registered = date_i18n( "M m, Y", strtotime( get_the_author_meta( 'user_registered', $user_ID ) ) ); echo 'Member since ' . $registered; ?>
Thank you 🙂