Relations between Milestones
Relations between milestones are defined by parent-child relationships.
If we change the kick-off date in the above case, the delivery milestone and steel cutting milestone dates will move while maintaining the lag difference between the different milestones as indicated.
This means that you can build a network of “fixed” relations with the important dates that should move and are typically related to payments critical operations or intermediate goals you want to meet in your projects.
The next step would typically be to add the task to this network.
Moving the kick-off milestone will move the milestones with their fixed lag. As can be seen below the lag takes account for weekends and holidays.
We can also notice that the early start ends late finish date will remain consistent with the milestones. Task start and finish date, however, will only move if obliged so. In the above case moving the milestones to a later date eliminates the margin on the task "purchase".
Moving the "kick-off" date to an earlier date will still keep the same lag between milestones but this time the tasks are pushed from the right to the left. The earliest dates of these tasks remain their consistency with the milestones and now show off their margin as earliest margin only.
Moving an intermediate milestone
Moving an intermediate milestone will have a different effect task on the right side see their margin reduced to zero. The delivery milestone has been forced to move which increased the overall project duration from 23 to 27 days while the task on the left see their margins on latest finish dates increased.