backup (export) failure, time exceeded

I am trying to backup by blog (cultureby.com) by exporting it. But I get this error message

<b>Fatal error</b>: Maximum execution time of 30 seconds exceeded in <b>/home/grant27/public_html/site/wp-includes/formatting.php</b> on line <b>306</b>
.

Could you please tell me what I can do to fix it.

Thanks.

Grant