There are 60 seconds in every Minute and 60 minutes in every Hour, but how many hours in each Primavera P6 Day?
Most days for most people have 24 hours in them, but not every day has 24 hours in it. On the day the clocks go forward, such as the start of British Summertime, it ends up with just 23 hours in it. The clocks move backwards again at the end of British Summertime and the day has 25 hours in it.
When it comes to project scheduling we need the length of a Day to be consistent. The same goes for a Week, a Month and even a Year. This post looks at how Primavera P6 achieves this and just what a Primavera P6 day actually is.
How Long Is A Primavera P6 Day?
The short answer is a Primavera P6 Day is as long as it has been configured to be. Primavera P6 can be set up so everyone uses exactly the same definition for each Time Period or they use one assigned to the Calendar in use at the time.
The following screenshot shows this P6 system uses the value of Time Periods set against the Calendar in use. This is done by selecting the Use assigned calendar to specify the number of work hours for each time period option as shown. This means the value of a Primavera P6 Day is determined by each P6 Calendar. When this option is not selected, the definition of a Primavera P6 Day is the same throughout the database.
There is a Time Periods button that displays the same set of four boxes for each Calendar. It is used to enter the number of hours for each Time Period.
In the graphic above, which is the system default, a Day is 8 Hours, a Week is 40 Hours, a Month is 172 Hours and a Year is 2000 Hours.
This means when I enter a duration of 3d for 3 Days, P6 will multiply it by 8 Hours per Day to get 24 Hours. It then stores this in the database in minutes as 24 Hours times 60 Minutes is 1440 Minutes.
Setting The Number of Hours For Each Time Period
I have come across many implementations of P6 where the values for Time Periods don’t make sense. I wouldn’t use the same values as the Primavera defaults. I now make use of the following procedure for setting the Hours for each Time Period.
The first step is to decide how many hours there are in a Day and the number of working days in a Week. Here in the UK, we have 7.5 hours in each working day and we work 5 days a week. The USA also works 5 days a week, but they normally count 8 hours in their working day.
Once the standard hours for a working day and number of days in a working week have been agreed, follow the following procedure:
- Hours/Day – set to the standard hours per day
- Hours/Week – multiply the *Hours/Day* by the standard number of working days in a week and set this to the result
- Hours/Month – this becomes the result of multiplying the *Hours/Day* by a sliding scale of days in an “average” month according to the number of working days per week as follows:
- 30 days in a month for 7 day working week
- 26 days in a month for 6 day working week
- 22 days in a month for 5 day working week
- 18 days in a month for 4 day working week
- 14 days in a month for a 3 day working week
- 9 days in a month for a 2 day working week
- 5 days in a month for a 1 day working week
- Hours/Year- the result of multiplying *Hours/Week* by 52
A Worked Example for the USA
Let’s assume we are in the USA and have 8 hours in the standard working day and 5 days in a week. Using the procedure gives us:
- Hours/Day is set to 8 hours
- Hours/Week is set to 40 hours, which is the result of multiplying the 5 days in a week by the 8 Hours/Day
- Hours/Month is set to 175 hours, which is the result of multiplying the 8 Hours/Day by the 22 days for a 5 day working week
- Hours/Year is set to 2080 hours, which is the result of multiplying 40 Hours/Week by 52 weeks in a year
A Worked Example for the UK
Let’s assume we are in the UK and have 7.5 hours in the standard working day and 5 days in a week. Using the procedure gives us:
- Hours/Day is set to 7.5 hours
- Hours/Week is set to 37.5 hours, which is the result of multiplying the 5 days in a week by the 7.5 Hours/Day
- Hours/Month is set to 165 hours, which is the result of multiplying the 7.5 Hours/Day by the 22 days for a 5 day working week
- Hours/Year is set to 1950 hours, which is the result of multiplying 37.5 Hours/Week by 52 weeks in a year
What Are The Time Period Abbreviations?
Primavera P6 provides abbreviations for Minutes (n), Hours (h), Days (d), Weeks (w), Months (m) and Years (y). These are used when entering durations so 3w means 3 Weeks, 5m means 5 Months and so forth.
It is possible for the P6 System Administrator to change these abbreviations, though I have never seen it done.
Which Calendar Is Used For Time Period Values?
The durations on Activities always use the Calendar assigned to the Activity. Entering durations, such as a Lag on a Resource Assignment uses the Calendar associated with the Resource for Resource Dependent Activity Types and the Activity Calendar for all others. When a Role is assigned without a Resource to the Resource Assignment, the Activity Calendar is always used.
The Calendar used in relationship lags is determined by the Calendar for scheduling Relationship Lag option set in the Scheduling Dialog.
About Barrie Callender
For 30 years, Barrie has worked exclusively in the Project Management industry. He has considerable experience, knowledge and skills implementing enterprise project management systems across many industries. His experience in fulfilling numerous roles includes, mentoring, training, workshops, project support, process and tool implementations, working through a PMO right up to full-blown Change Management Programs. He has in-depth knowledge of Primavera P6, Microsoft Project, Deltek Cobra, Oracle Projects. He is a member of the APM Thames Valley Branch and, both the Governance SIG and the Planning, Monitoring & Control SIG.