Fix calendar grid alignment when doesn't start on Monday

README.md

@@ -224,6 +224,10 @@ Copy the `team51-focal-point` folder to your `mu-plugins` directory.
 
 ## Changelog
 
+### 2.1.3
+
+- **Calendar grid alignment:** fixed month grid date placement when WordPress **Week Starts On** is set to Sunday (or any `start_of_week` other than Monday). Dates and events now appear under the correct weekday column.
+
 ### 2.1.2
 
 - **Calendar loading UX:** added a loading skeleton while calendar month requests are in flight.

package.json

@@ -1,6 +1,6 @@
 {
     "name": "wpcomsp-simple-events",
-    "version": "2.1.2",
+    "version": "2.1.3",
     "description": "A simple Gutenberg-first event management plugin that integrates with WooCommerce Box Office.",
     "author": {
         "name": "WordPress.com Special Projects Team",

plugin.php

@@ -3,7 +3,7 @@
  * Simple Events Plugin bootstrap file.
  *
  * @since       1.0.0
- * @version     2.1.2
+ * @version     2.1.3
  * @author      WordPress.com Special Projects
  * @license     GPL-3.0-or-later
  *
@@ -14,7 +14,7 @@
  * Description:             Event management frontend for WooCommerce Box Office.
  * Requires at least:       6.5
  * Tested up to:            6.9
- * Version:                 2.1.2
+ * Version:                 2.1.3
  * Requires PHP:            8.0
  * Author:                  WordPress.com Special Projects
  * Author URI:              https://wpspecialprojects.wordpress.com
@@ -32,7 +32,7 @@
 function_exists( 'get_plugin_data' ) || require_once ABSPATH . 'wp-admin/includes/plugin.php';
 define( 'SE_METADATA', get_plugin_data( __FILE__, false, false ) );
 
-define( 'SE_VERSION', '2.1.2' );
+define( 'SE_VERSION', '2.1.3' );
 define( 'SE_BASENAME', plugin_basename( __FILE__ ) );
 define( 'SE_PLUGIN_DIR', untrailingslashit( plugin_dir_path( __FILE__ ) ) );
 define( 'SE_PLUGIN_URL', untrailingslashit( plugin_dir_url( __FILE__ ) ) );

src/classes/class-se-calendar.php

@@ -60,7 +60,7 @@ public function register_routes(): void {
 	 * @param string $format The display format for the days of the week.
 	 *
 	 * @return array Days of the week.
-	 **@category Events
+	 * *@category Events
 	 */
 	public function simple_events_get_days_of_week( $format = null ) {
 		global $wp_locale;
@@ -442,56 +442,48 @@ private function get_events_by_date( $date ): array {
 
 
 	/**
-	 * Get the start day based on the given date and start of the week.
+	 * Get the first calendar cell for the month (weeks align to WordPress start of week).
 	 *
-	 * @param mixed   $date          The date for which to calculate the start day.
-	 * @param integer $start_of_week The start of the week (0-6, where 0 is Sunday).
+	 * @param mixed   $date          First day of the month to display.
+	 * @param integer $start_of_week Attribute `start_of_week` option: 0 = Sunday through 6 = Saturday.
 	 *
-	 * @return DateTime The start day based on the given date and start of the week.
+	 * @return DateTime First grid day at 00:00:00.
 	 */
 	private function get_start_day( $date, $start_of_week ) {
-		$start_date         = clone $date;
-		$start_day_interval = 0;
+		$start_date = clone $date;
+		$start_date->setTime( 0, 0, 0 );
 
-		$start_day_week_position = $date->format( 'w' );
+		$w                = (int) $start_date->format( 'w' );
+		$days_back_to_sow = ( $w - (int) $start_of_week + 7 ) % 7;
 
-		if ( $start_of_week > 0 && 0 === intval( $start_day_week_position ) ) {
-			$start_day_week_position = 7;
-		}
-
-		if ( 0 !== intval( $start_day_week_position ) ) {
-			$start_day_interval = abs( 1 - $start_day_week_position );
-		}
-
-		return $start_date->sub( new DateInterval( 'P' . $start_day_interval . 'D' ) );
+		return 0 === $days_back_to_sow
+			? $start_date
+			: $start_date->sub( new DateInterval( 'P' . $days_back_to_sow . 'D' ) );
 	}
 
 
 	/**
-	 * Get the end day based on the given date and start of the week.
+	 * Get the last day shown in the grid for the month (inclusive), at 23:59:59.
 	 *
-	 * @param Date    $date          The date to calculate the end day from.
-	 * @param integer $start_of_week The start of the `week (0-6, where 0 is Sunday).
+	 * @param mixed   $date          Any day in the month (used to find last day of month).
+	 * @param integer $start_of_week Attribute `start_of_week` option: 0 = Sunday through 6 = Saturday.
 	 *
-	 * @return DateTime The end day based on the given date and start of the week.
+	 * @return DateTime End boundary for the period.
 	 */
 	private function get_end_day( $date, $start_of_week ) {
-		$end_date          = clone $date;
-		$last_day_interval = 0;
+		$end_date = clone $date;
+		$end_date->modify( 'last day of this month' );
+		$end_date->setTime( 0, 0, 0 );
 
-		$last_day_of_month      = $end_date->modify( 'last day of this month' );
-		$last_day_week_position = $last_day_of_month->format( 'w' );
+		$w             = (int) $end_date->format( 'w' );
+		$offset_in_row = ( $w - (int) $start_of_week + 7 ) % 7;
+		$days_to_add   = 6 - $offset_in_row;
 
-		if ( $start_of_week > 0 && 0 === intval( $last_day_week_position ) ) {
-			$last_day_week_position = 7;
+		if ( $days_to_add > 0 ) {
+			$end_date->add( new DateInterval( 'P' . $days_to_add . 'D' ) );
 		}
-
-		if ( 0 !== intval( $last_day_week_position ) ) {
-			$last_day_interval = 7 - $last_day_week_position;
-		}
-
 		$end_date->setTime( 23, 59, 59 );
 
-		return $end_date->add( new DateInterval( 'P' . $last_day_interval . 'D' ) );
+		return $end_date;
 	}
 }