Read the comments of this post !
44) Finish the faculty !
How That cronjobs works ??!!
The answer is very easy : it depends on the visitors of the site when any visitor come to your site it checks the existing time and the execution time : if execution time is less than existing time it start the execution operation, if not there is no execution.
It makes the site run little slow if you used this way , so using cronjobs manager in cpanel is very effective .