Go to the Windows ribbon and select Animation Editor.
Move the Focus Time Marker in the Gantt Window to the date you wish the animation to begin. Left click in the Focus Time Channel to define the start of the animation by creating a Focus Time Key (Yellow Diamond) at 0:00:00. Move the Focus Time Marker in the Gantt Window to the date you wish the animation to finish. Scroll out in the Animation Editor Window to see the duration you wish the animation to end. Left click at the desired time in the Focus Time Channel to define the length of the animation.