WordPress 全站置灰并定时关闭

add_action('wp_footer',function(){
	$show = date_diff(date_create("2022-12-02"), date_create())->invert;
	if($show){
		echo <<<EOF
<style type="text/css">
html { 
	-webkit-filter: grayscale(100%);
	-moz-filter: grayscale(100%); 
	-ms-filter: grayscale(100%); 
	-o-filter: grayscale(100%); 
	filter: progid:DXImageTransform.Microsoft.BasicImage(grayscale=1);  
	_filter: none; 
}
</style>
EOF;
	}
});