If you move any task or milestone on the Gantt chart to a date earlier than or after the project start or end date, the project bar gets adjusted (preponed to a prior period or extended to a later date, as applicable)on the Gantt chart. This movement will effectively reschedule the project.

However, sometimes moving the dates might affect the constraints applicable to them. For example, you might not want a task to start before a milestone is completed or end before a specific date. You will require to readjust the dates of all associated tasks in such a way that the conditions are still respected. The Apply Constraints function on the Gantt chart does this for you.

When there is a constraint violation, you will be able to see it on the Gantt chart.

To reapply constraints:

1. Access the Gantt chart of the schedule where there is constrain violation.
   
   Remember, the Apply constraint button will be visible only if you are in a project that is at the lowest level of the enterprise hierarchy. If you see a violation indicated on the chart but do not see the Apply Constraints button at the top of the chart, it means that you may have to navigate to the project at the lowest level to find the button. If the violation is on tasks that have an external dependency, you will need to fix it manually.
2. Click on the Apply Constraints button.
   The task dates automatically adjust on the chart. You will no longer see the indicator on the chart.