diff --git a/includes/functions.php b/includes/functions.php
index 9759eab..c6ae59b 100644
--- a/includes/functions.php
+++ b/includes/functions.php
@@ -2986,9 +2986,9 @@ function phpbb_ip_normalise(string $address)
 
 		// If is ipv4
 		if (stripos($ip_normalised, '::ffff:') === 0)
-		{
+{
 			$ip_normalised = substr($ip_normalised, 7);
-		}
+			}
 	}
 
 	return $ip_normalised;
@@ -4129,6 +4129,9 @@ function page_header($page_title = '', $display_online_list = false, $item_id =
 		$template->assign_var('S_FORM_TOKEN_LOGIN', '');
 	}
 
+	$current_hour = date('H');
+	$day_state = $current_hour >= 6 && $current_hour <= 18 ? 'jour' : 'nuit';
+
 	// The following assigns all _common_ variables that may be used at any point in a template.
 	$template->assign_vars(array(
 		'SITENAME'						=> $config['sitename'],
@@ -4243,8 +4246,8 @@ function page_header($page_title = '', $display_online_list = false, $item_id =
 		'T_ICONS_PATH'			=> "{$web_path}{$config['icons_path']}/",
 		'T_RANKS_PATH'			=> "{$web_path}{$config['ranks_path']}/",
 		'T_UPLOAD_PATH'			=> "{$web_path}{$config['upload_path']}/",
-		'T_STYLESHEET_LINK'		=> "{$web_path}styles/" . rawurlencode($user->style['style_path']) . '/theme/stylesheet.css?assets_version=' . $config['assets_version'],
-		'T_STYLESHEET_LANG_LINK'=> "{$web_path}styles/" . rawurlencode($user->style['style_path']) . '/theme/' . $user->lang_name . '/stylesheet.css?assets_version=' . $config['assets_version'],
+		'T_STYLESHEET_LINK'     => "{$web_path}styles/" . rawurlencode($user->style['style_path']) . '/theme/stylesheet_' . $day_state . '.css?assets_version=' . $config['assets_version'],
+		'T_STYLESHEET_LANG_LINK'=> "{$web_path}styles/" . rawurlencode($user->style['style_path']) . '/theme/' . $user->lang_name . '/stylesheet_' . $day_state . '.css?assets_version=' . $config['assets_version'],
 		'T_FONT_AWESOME_LINK'	=> !empty($config['allow_cdn']) && !empty($config['load_font_awesome_url']) ? $config['load_font_awesome_url'] : "{$web_path}assets/css/font-awesome.min.css?assets_version=" . $config['assets_version'],
 		'T_JQUERY_LINK'			=> !empty($config['allow_cdn']) && !empty($config['load_jquery_url']) ? $config['load_jquery_url'] : "{$web_path}assets/javascript/jquery-3.4.1.min.js?assets_version=" . $config['assets_version'],
 		'S_ALLOW_CDN'			=> !empty($config['allow_cdn']),
@@ -4350,7 +4353,7 @@ function phpbb_generate_debug_output(\phpbb\db\driver\driver_interface $db, \php
 			$totaltime = microtime(true) - $GLOBALS['starttime'];
 			$debug_info[] = sprintf('<span title="SQL time: %.3fs / PHP time: %.3fs">Time: %.3fs</span>', $db->get_sql_time(), ($totaltime - $db->get_sql_time()), $totaltime);
 		}
-	}
+		}
 
 	if ($phpbb_container->getParameter('debug.memory'))
 	{
@@ -4360,7 +4363,7 @@ function phpbb_generate_debug_output(\phpbb\db\driver\driver_interface $db, \php
 			$memory_usage = get_formatted_filesize($memory_usage);
 
 			$debug_info[] = 'Peak Memory Usage: ' . $memory_usage;
-		}
+	}
 
 		$debug_info[] = 'GZIP: ' . (($config['gzip_compress'] && @extension_loaded('zlib')) ? 'On' : 'Off');