WordPress is coded mainly in PHP programming language. To protect web servers from abuse, there is a time limit set for how long a PHP script can run.
Some WordPress hosting providers have set this value to a higher level while others may have set it to a lower level. When a script reaches the maximum execution time limit, it results into maximum execution time exceeded error.
Editing .htaccess File Manually by adding “php_value max_execution_time 300” Using a Plugin