diff -r be944660c56a -r 3d72ae0968f4 wp/wp-includes/blocks/calendar.php
--- a/wp/wp-includes/blocks/calendar.php	Wed Sep 21 18:19:35 2022 +0200
+++ b/wp/wp-includes/blocks/calendar.php	Tue Sep 27 16:37:53 2022 +0200
@@ -15,6 +15,15 @@
 function render_block_core_calendar( $attributes ) {
 	global $monthnum, $year;
 
+	// Calendar shouldn't be rendered
+	// when there are no published posts on the site.
+	if ( ! block_core_calendar_has_published_posts() ) {
+		if ( is_user_logged_in() ) {
+			return '<div>' . __( 'The calendar block is hidden because there are no published posts.' ) . '</div>';
+		}
+		return '';
+	}
+
 	$previous_monthnum = $monthnum;
 	$previous_year     = $year;
 
@@ -59,3 +68,86 @@
 }
 
 add_action( 'init', 'register_block_core_calendar' );
+
+/**
+ * Returns whether or not there are any published posts.
+ *
+ * Used to hide the calendar block when there are no published posts.
+ * This compensates for a known Core bug: https://core.trac.wordpress.org/ticket/12016
+ *
+ * @return bool Has any published posts or not.
+ */
+function block_core_calendar_has_published_posts() {
+	// Multisite already has an option that stores the count of the published posts.
+	// Let's use that for multisites.
+	if ( is_multisite() ) {
+		return 0 < (int) get_option( 'post_count' );
+	}
+
+	// On single sites we try our own cached option first.
+	$has_published_posts = get_option( 'wp_calendar_block_has_published_posts', null );
+	if ( null !== $has_published_posts ) {
+		return (bool) $has_published_posts;
+	}
+
+	// No cache hit, let's update the cache and return the cached value.
+	return block_core_calendar_update_has_published_posts();
+}
+
+/**
+ * Queries the database for any published post and saves
+ * a flag whether any published post exists or not.
+ *
+ * @return bool Has any published posts or not.
+ */
+function block_core_calendar_update_has_published_posts() {
+	global $wpdb;
+	$has_published_posts = (bool) $wpdb->get_var( "SELECT 1 as test FROM {$wpdb->posts} WHERE post_type = 'post' AND post_status = 'publish' LIMIT 1" );
+	update_option( 'wp_calendar_block_has_published_posts', $has_published_posts );
+	return $has_published_posts;
+}
+
+// We only want to register these functions and actions when
+// we are on single sites. On multi sites we use `post_count` option.
+if ( ! is_multisite() ) {
+	/**
+	 * Handler for updating the has published posts flag when a post is deleted.
+	 *
+	 * @param int $post_id Deleted post ID.
+	 */
+	function block_core_calendar_update_has_published_post_on_delete( $post_id ) {
+		$post = get_post( $post_id );
+
+		if ( ! $post || 'publish' !== $post->post_status || 'post' !== $post->post_type ) {
+			return;
+		}
+
+		block_core_calendar_update_has_published_posts();
+	}
+
+	/**
+	 * Handler for updating the has published posts flag when a post status changes.
+	 *
+	 * @param string  $new_status The status the post is changing to.
+	 * @param string  $old_status The status the post is changing from.
+	 * @param WP_Post $post       Post object.
+	 */
+	function block_core_calendar_update_has_published_post_on_transition_post_status( $new_status, $old_status, $post ) {
+		if ( $new_status === $old_status ) {
+			return;
+		}
+
+		if ( 'post' !== get_post_type( $post ) ) {
+			return;
+		}
+
+		if ( 'publish' !== $new_status && 'publish' !== $old_status ) {
+			return;
+		}
+
+		block_core_calendar_update_has_published_posts();
+	}
+
+	add_action( 'delete_post', 'block_core_calendar_update_has_published_post_on_delete' );
+	add_action( 'transition_post_status', 'block_core_calendar_update_has_published_post_on_transition_post_status', 10, 3 );
+}