There are situations where drupal you want to assign a particular role to a user after he/she has been registered for a period of time. This functionality might be needed for situations where you want a user to get permission to perform a particular task on your site.
This functionality can be fulfilled by Role Delay module. Role Delay provides an option to associate a particular amount of time to each role on edit role page. strtotime() can be used to provide time.
This module can be used for social or blogging sites where you want to assign a role to users who has been on your site for sufficient amount of time.