Sometimes a project you are scheduling in Primavera P6 does not have an approved start date or the start date is unknown. To avoid confusion in these situations, many folks don’t want to display calendar dates on the Gantt chart. Instead they want to plan using calendar ordinal dates.
In most scheduling situations you have a known project start date and, possibly, a project deadline. But if you have a project that has to go through an involved approval process, it might not have a specified start date. If this is the case, stakeholders may become confused when you present them a Gantt chart that has a calendar start date, and measures progress from that date on a calendar.
It makes more sense to make the start date zero and plan in a series: 1, 2, 3, 4… The series you define can be in days, weeks, or even months. This series of dates are referred to, using a rather cryptic name, as ordinal dates. Primavera P6 is capable of displaying ‘calendar’ ordinal dates on the Gantt chart, in lieu of not having a specified project start date.
This article demonstrates how to display calendar ordinal dates on the Gantt chart. It is beyond the scope of this article to show how to display a calendar ordinal date columns in the activities table.
We have in Figure 1 our demonstration project.
The project has a start date of 05-Sep-2016. The Gantt chart displays the progress of the schedule through the month of September and on into October. Let’s assume this project is in the initial planning and/or development stage and does not have an assigned calendar start date. How can we present the schedule to stakeholders in a way that does not lead them to believe the project start date is 05-Sep-2016?
Let’s investigate our options by right clicking on the timescale and selecting Timescale from the pop up menu, Figure 2.
The resulting timescale dialog is displayed in Figure 3.
Currently the timescale format is set to display three lines. The date format is ‘week/day 1’. Change the timescale toggle to two lines. Do not show or uncheck the ‘show primary dates’ toggle. Toggle the ‘show ordinal dates’ option. Set the ordinal start to PS, which is the project start date. Make the ordinal interval week. Your Timescale dialog should look similar to Figure 4.
Click OK and the resulting Gantt chart is as displayed in Figure 5. In the Figure 5 Gantt chart we see that the project commences on day zero and proceeds in a series with weekly intervals.
Now change the ordinal date interval to day. The resulting Gantt chart is displayed in Figure 6.
We can even change the ordinal date interval to month, quarter, or year. Looks like for our schedule an ordinal date interval of week is most appropriate. It is possible to display both calendar days and ordinal calendar days on the Gantt chart. To do this for our schedule, in the timescale dialog, toggle three lines for the timescale format. Toggle show primary dates and select calendar type and ‘week/day 1’ date interval, Figure 7.
The resulting Gantt chart is in figure 8.
As demonstrated in Figure 8, it is possible to display both calendar dates and ordinal calendar dates on a Gantt chart.
When a project is in the planning stage it might not have an assigned start date and deadline. If this is the situation than it is best to display ordinal calendar dates on the Primavera P6 Gantt chart. You also may need to remove the start and finish columns in the activities table, again, to avoid confusion. It is possible, but somewhat involved, to display a calendar ordinal weeks column in the activities table.
One approach is to use user defined fields and implement the P6 global change tool to compute the ordinal days and/or ordinal weeks. The problem with this approach is that the global change computation only accounts for working days, and not the weekends.
Because of this, the ordinal columns in the activities table will not correspond to the ordinal calendar dates on the Gantt chart. This is also why we distinguish between ordinal dates and ordinal calendar dates; the ordinal ‘calendar’ dates include weekends in their computation.
Again, there is an approach for displaying ordinal calendar weeks in a column on the activity table, but it requires exporting the schedule to Microsoft Excel, and making editing changes to your data in Microsoft Excel. The simpler approach is to simply display ordinal calendar dates on your Gantt chart and not display a start and finish column on the activities table.