I would like your help with the stages to changing the baseline dates in P6.

In P6 you create your schedule and then take a baseline (snapshot) of the schedule at a point in time. You use that baseline as your point of reference and the dates usually should not be changed. You are able to update the baseline dates in a baseline. You can do this in the same area you take the baseline by using "update baseline". It will take actuals and replace old baseline dates as well as new planned dates will replace the old baseline dates. Using the Update Baseline utility, you can update the original baseline plan with new activity, resource/role assignment, and project data. When updating a baseline, you can choose to update all activities or you can apply a filter to update activities that meet the filter’s criteria. You can also specify the types of data to update, including specific data related to activities, resources, costs, thresholds, and issues.