How lead/lag is handled when you export to another project management application

In Powerproject, a link can have lead/lag at the start of the link, at the end of the link, or at both ends of the link. The lead/lag at the start of a link is calculated according to the predecessor task's calendar and the lead/lag at the end of a link is calculated according to the successor task's calendar. Where the predecessor and successor tasks use different calendars, the ability to position lead/lag at the start or the end of a link enables you to obtain precise and accurate positioning of tasks when you reschedule a project.

Other project management applications, such as Microsoft® Project and Primavera P6®, only allow lead/lag to be present at one end of a link. If a link in Powerproject has lead/lag on both the start and the end of the link, the two values are combined into a single value during export.

The calendar that is used to resolve the lead/lag on a link differs from one application to another, as explained below.

Microsoft Project

Lead/lag is always calculated according to the successor task's calendar.

Primavera P6

Has a global option, the setting of which determines whether lead/lag is calculated according to the predecessor task's calendar, the successor task's calendar, or a 24 hour, elapsed time calendar.

In projects that are imported from Microsoft Project, lead/lag on links between tasks that use different calendars is calculated using the successor task's calendar. In addition to this, if a Microsoft Project file contains any links between tasks that use different calendars that have their lead/lag defined in terms of percentage rather than in terms of duration, this percentage lead/lag is converted to a fixed duration when the project is imported into Powerproject.

As the calendar that is used to calculate the lead/lag is configurable in Primavera P6, you must find out how this setting is configured in the Primavera software before you export a Powerproject project to be opened in either of these applications, so that you can specify the same setting during the export process - using the Calendar for link lag group on the Primavera XML & XER Export Options dialog:

  • If you calculate lead/lag using the predecessor task's calendar in Primavera P6, select the Predecessor radio button when exporting a project.
  • If you calculate lead/lag using the successor task's calendar in Primavera P6, select the Successor radio button when exporting a project.
  • If you calculate lead/lag using the 24 hour, elapsed time calendar in Primavera P6, select the 24 Hour radio button when exporting a project.

Selecting the wrong calendar option during the export process may result in the project rescheduling incorrectly once it has been exported.

This is illustrated by the simple project below:

Tasks positioned precisely using lead/lag

The project is exported. During the export process, the Predecessor radio button is selected in the Calendar for link lag group on the Primaver XML & XER Export Options dialog.

If, when the exported project is opened in Primavera P6, Predecessor Activity Calendar is selected in Advanced Schedule Options, the lead/lag is calculated according to the correct calendar (because the correct calendar option was selected during the export process), giving the correct results:

Predecessor Activity Calendar selected for scheduling relationship lag

However, if when the project is opened in Primavera P6, Successor Activity Calendar is selected in Advanced Schedule Options, the lead/lag is calculated according to the wrong calendar (because the wrong calendar option was selected during the export process), giving incorrect results:

Successor Activity Calendar selected for scheduling relationship lag

In this example, the lead/lag would also be calculated according to the wrong calendar if 24 Hour Calendar was selected in Advanced Schedule Options.

Related Topics:

Lead/lag links between tasks with different calendars

Exporting projects to Microsoft Project

Exporting projects to Primavera software