How to delegate tasks to another person for a set period of time.
In SharePoint, locate the user name menu in the top right corner of the page.
From the drop-down menu, select Nintex Workflow 2013 > Task Delegation.
Select "Delegate tasks to a user between specific dates".
Select the date range for the delegations and who should be delegated the tasks during that period.
The scope can be changed to apply only to tasks from the current site, or the entire SharePoint farm.
Note: If a task is delegated to a user account, the long term delegation is ignored (so it is not delegated again).
This ability depends on the Global Setting “Long term delegation”. Site administrators can set up long term delegation for other user accounts if the Global Setting “Site administrators long term delegation” is enabled. For more information regarding task delegation, see All things Delegation