Not possible to translate date suffixes in WordPress

Overview of the issue

Some  themes or plugins use the wp_date() or date_i18n() WordPress functions to display dates. These dates may use a suffix as 1st or 26th, depending on the parameters selected.

Currently, it’s not possible to translate date suffixes because of a longstanding known limitation in WordPress core.

Workaround

As a workaround, you can use the wp_date filter to get the date, then modify the suffix before it’s rendered on the page. Please make a full backup of your site before proceeding and follow the steps below:

• Add the following code to the functions.php file of your theme:
  
  Translate date suffixes in WordPress

  function wpmldp_translate_date_format( $date ) {	
  	
  	//Create array with dates
  	$month_dates = array();
  	$month_dates[] = '1st';
  	$month_dates[] = '2nd';
  	$month_dates[] = '3rd';
  	for($d=4; $d<=30; $d++) {
  		$month_dates[] = $d.'th';
  	}
  	$month_dates[] = '31st';
  
  	//Register strings on String Translator
  	foreach( $month_dates as $month_date ) {
  		do_action( 'wpml_register_single_string', 'Date Formats', 'Month Date (WPML) - '.$month_date, $month_date);
  	}	
  	
  	//Translate strings
  	if( in_array($date, $month_dates) ) {
  		$date = apply_filters( 'wpml_translate_single_string', $date, 'Date Formats', 'Month Date (WPML) - '.$date);
  	}
  	
  
  	return $date;
  }
  add_filter( 'wp_date', 'wpmldp_translate_date_format', 10, 1 );

• Open the page where the dates are displayed. This will execute the filter added.
• Go to WPML → String Translation and translate the dates.
•  You will need to translate each suffix separately (e.g. 1st, 2nd…) because it may change depending on the language.