Time Unit configuration

The definition and configuration of time unit on P6 has been a matter of misunderstanding. This a blog post about it with a concepts clarification and a configuration preview example.

Although we can define the Time units in Hours, Days, Weeks, Months or Years but P6 stores the time unit values in HOURS in the database. Then it can be displayed in Days, Weeks etc. The conversion between different units of time is carried out based on the conversion defined in Admin > Admin Preferences > Time Periods Tab. There we can define Hours/Day, Hours/Week and Hours/Year. This can be defined only by administrators. There is a checkbox “Use assigned calendar to specify the number of work hours for each time period”. It is advised to keep this checkbox checked if the working hours/day in an individual calendar is not same to that defined in Admin Preferences. Because if the Original Duration for an activity is defined in hours and the time units are displayed in “Days” or “Months” then there might be some inaccurate display. Let us understand this by an example;

Let us set 8 hours/day in the Admin > Admin Preferences > Time Periods Tab. The checkbox “Use assigned calendar to specify the number of work hours for each time period” is unchecked. Now define a calendar and keep the Working Hours per day = 12 (contrary to what we defined in Admin Preferences). Now insert an activity. Go to Edit > User Preferences > Time Units Tab, and Change the Duration Format to Hour. Enter the activity duration as 41 hours (i.e. we defined an activity which has duration of 41 hours and the calendar assigned has 12 hours/day as working hours). Now change the duration format to Days. By calculation, we should have 41/12 = 3.42 days. But we can see that P6 has calculated it as 5.13 days (i.e. 41/8=5.13). It means that P6 is still using the conversion defined in the Admin Preferences which is wrong because in calendar we have 12 working hours/day. This problem can be avoided if checkbox “Use assigned calendar to specify the number of work hours for each time period” is kept checked in Admin Preferences.