just for the idea, 1. you have to create extra custom fields on the Opportunity object for saving the days passed in each Stage, 2. and then you have to monitor the value change of Stage, 3. calculate the days passed and insert the result into the custom field
for monitor the value change of Stage, you can use Workflow or Trigger
1. you have to create extra custom fields on the Opportunity object for saving the days passed in each Stage,
2. and then you have to monitor the value change of Stage,
3. calculate the days passed and insert the result into the custom field
for monitor the value change of Stage, you can use Workflow or Trigger