diff -r c7c34916027a -r 177826044cd9 wp/wp-includes/blocks/calendar.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/blocks/calendar.php	Mon Oct 14 18:28:13 2019 +0200
@@ -0,0 +1,75 @@
+<?php
+/**
+ * Server-side rendering of the `core/calendar` block.
+ *
+ * @package WordPress
+ */
+
+/**
+ * Renders the `core/calendar` block on server.
+ *
+ * @param array $attributes The block attributes.
+ *
+ * @return string Returns the block content.
+ */
+function render_block_core_calendar( $attributes ) {
+	global $monthnum, $year;
+
+	$previous_monthnum = $monthnum;
+	$previous_year     = $year;
+
+	if ( isset( $attributes['month'] ) && isset( $attributes['year'] ) ) {
+		$permalink_structure = get_option( 'permalink_structure' );
+		if (
+			strpos( $permalink_structure, '%monthnum%' ) !== false &&
+			strpos( $permalink_structure, '%year%' ) !== false
+		) {
+			// phpcs:ignore WordPress.WP.GlobalVariablesOverride.OverrideProhibited
+			$monthnum = $attributes['month'];
+			// phpcs:ignore WordPress.WP.GlobalVariablesOverride.OverrideProhibited
+			$year = $attributes['year'];
+		}
+	}
+
+	$custom_class_name = empty( $attributes['className'] ) ? '' : ' ' . $attributes['className'];
+	$align_class_name  = empty( $attributes['align'] ) ? '' : ' ' . "align{$attributes['align']}";
+
+	return sprintf(
+		'<div class="%1$s">%2$s</div>',
+		esc_attr( 'wp-block-calendar' . $custom_class_name . $align_class_name ),
+		get_calendar( true, false )
+	);
+
+	// phpcs:ignore WordPress.WP.GlobalVariablesOverride.OverrideProhibited
+	$monthnum = $previous_monthnum;
+	// phpcs:ignore WordPress.WP.GlobalVariablesOverride.OverrideProhibited
+	$year = $previous_year;
+}
+
+/**
+ * Registers the `core/calendar` block on server.
+ */
+function register_block_core_calendar() {
+	register_block_type(
+		'core/calendar',
+		array(
+			'attributes'      => array(
+				'align'     => array(
+					'type' => 'string',
+				),
+				'className' => array(
+					'type' => 'string',
+				),
+				'month'     => array(
+					'type' => 'integer',
+				),
+				'year'      => array(
+					'type' => 'integer',
+				),
+			),
+			'render_callback' => 'render_block_core_calendar',
+		)
+	);
+}
+
+add_action( 'init', 'register_block_core_calendar' );