Gantt chart visually communicates when decisions will be implemented. This definition from Business Dictionary provides added discussion:
Type of bar-chart that shows both the scheduled and completed work over a period. A time-scale is given on the chart's horizontal axis and each activity is shown as a separate horizontal rectangle (bar) whose length is proportional to the time required (or taken) for the activity's completion. In project planning, these charts show start and finish dates, critical and non-critical activities, slack time, and predecessor-successor relationships. Also called chronogram, it was invented in 1917 by the US engineer and a scientific-management pioneer, Henry L. Gantt (1861-1919).
Also, this site provides examples and more discussion.
Finally, under the heading "Secondary Sources" in the right menu, if you click on the "Excel" link, then you will find a website that will provide instructions of how to create a Gantt chart using Excel. If you search "Gantt," "chart,' and "Excel," then you will find other sources.