The If an item has been in a workflow stage only once, the date associated with a workflow stage for any given work item that stage is the date the item entered that workflow stage. If an item has been in a workflow stage more than once, the date associated with that stage is the last date the item entered each the workflow stepstage.
Detailed Information
If an item is moved backwards in the flow, say from step C to step B, it is considered never to have been in step C at all. All of the time in step C will be added to the time in step B. It will get a new timestamp for step C when it reenters that workflow stage.
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