On Work Orders, in the Schedule section, there are four different date types: 

Request Date: This date will auto-populate with the current date and time when a Work Order is created by a user or the system via a PM, PdM, or Job Plan. When a Work Order is created via approving a Work Request, the Request Date will be copied from the Work Request Date field. Request Date represents the time when the Work Order/ Request was created, although users may manually change this date while editing.
 
Requested Start and Finish: These dates can auto-populate depending on the origin of the Work Order. If a Work Order is created by an approved Work Request, the Requested Start and Finish will be copied. Requested Start and Finish represent the ideal window for the Work Order to be completed. Please see the Completion Window‍ article for more information on how this field is calculated on PM Work Orders.
 
Scheduled Start and Finish: This date will auto-populate when Estimated Labor is added to a Work Order manually using the Scheduler, or via a PM. A Work Setting will also allow this to be populated with the Completion Window. Scheduled Start and Scheduled Finish represent the ideal window of time the actual task will be performed and completed by a specific person(s).
 
Actual Start and Finish: This date will auto-populate when Actual Labor is added or if the Work Order is Completed. In the Work Settings under Workflow, there are a few options to change how these fields are auto-populated. Actual Start and Finish represent the actual date and time the work began and was completed.