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Should activity durations always be in whole days? (P6)

19 replies [Last post]
Thu, 2018-11-01 12:02
A T
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Hello

I am just starting out in planning and I don't have much experience when it comes to estimating durations. 

My question is, is it best practice to use whole days when inputting activity durations? I understand that having fraction or decimals of days can cause activities with one day duration to span across two days etc. 

For example if you are working an 8 hour day and estimate an activity to take 10 hours then it will take one man approx 1.25 days. 

Should you always round your duration estimates up or down to whole days (3.2 days to 3 days or 5.7 days to 6 days) in order to be able to set the start and finish times of your activities to match the calendars start and finish times? 

Does the need to round up and down to whole days vary depending on the size and the length of the project? 

 

Thank you in advance. 

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Wed, 2018-11-07 13:43
#1
Zoltan Palffy
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glad I could help 

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Mon, 2018-11-05 16:18
#2
A T
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Thanks Zoltan

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Fri, 2018-11-02 13:13
#3
Zoltan Palffy
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already answered that 

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Fri, 2018-11-02 13:02
#4
A T
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Thank you Anoon 

Would you have any input on the below questions

http://www.planningplanet.com/forums/planning-scheduling-programming-discussion/711265/p6-calendar-changes-during-project 

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Fri, 2018-11-02 13:00
#5
Zoltan Palffy
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every make sure that the data date TIME is correct

make sure that all start milestones start at 8:00 am or the earliest time for that associated calendar

make sure that all finish milestones finish at 5:00 pm or the latest working time associated with that calendar.

going forward make sure that all actual start date times start at 8:00 am or the earliest time for that associated calendar

going forward make sure that all actual finish date times finish at 5:00 pm or the latest time for that associated calendar

make sure that original durations and remaining duration are in whole days. 

make sure that the project must finish by date TIME is set to 5:00 pm or the latest time for that associated calendar

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Fri, 2018-11-02 10:58
#6
Anoon Iimos
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No problem. Please note however that I'm referring to activity-specific calendars. You might be in conflict with your project and or global calendars, so you may need to detach the activities that need fixes. I haven't used P6 for quite some time, so I can't give specific steps, but I guess you cannot go wrong if you just understand the principles.
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Fri, 2018-11-02 07:55
#7
A T
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Anoon

Thank you for your help. I'll make the changes to everything right of the data date. I will be applying the changes in the next couple of days and I will let you know the results. 

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Fri, 2018-11-02 04:02
#8
Anoon Iimos
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To continue my comment below, again remember that you will only apply the fixes to all the activities spanning on the right of the data date. The calendars on the left of the data date maybe wrong but once activities were completed, calendars become irrelevant as you already have actual start and finish dates. Now, define a new calendar (exactly as what you wanted), and assign the new calendar to all the activities spanning on the right of the data date (but first you have to remove all calendars previously assigned before assigning the new calendar). After all the fixes, try to run the schedule (without moving the data date) and kindly give feedback to us or ask more questions. Regarding shifts and several crews utilized on one activity, you schedule it in hours. If you have defined correctly your calendars in terms of working and non working hours, then there's no reason that you will get wrong results or dates.
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Thu, 2018-11-01 19:49
#9
A T
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Thank you for the information Rafael I appreciate it. 

Would anyone be able to answer this question also? 

http://www.planningplanet.com/forums/planning-scheduling-programming-discussion/711265/p6-calendar-changes-during-project  

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Thu, 2018-11-01 17:53
#10
Rafael Davila
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There is no excuse for the scheduler not to take control of activity start time of day.  If an activity scheduled to take 8 hours took 10 hours it shall be scheduled and reported as such. When rounding durations resource costs might be pulled wrong ...

It is not necessary to round activity durations to take control of activity start and finish dates, it is wrong to do so.   This is a flawed workaround of some schedulers that either do not know how to tame start/finish time or when their software does not helps.

When working on large projects with thousands of activities daily time cards shall keep record exact number of work hours per activity but not time of day. From these start time of activity can be estimated. If predecessor activity finished such day and only 2 work hours/employee are reported you can estimate finish time to be 2hrs after start of day.  If successor finished such day and 6 hours are reported you can estimate finish time to be 2hrs+6hrs=8hrs after start of day.  You can go the easy/pragmatic way and estimate first half of day for work on predecessor and the remaining for work on successor. 

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Thu, 2018-11-01 16:38
#11
A T
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Rafael

Is it always possible to record the start and finish times for each activity? When working on large projects with thousands of activities it would be very difficult to record start and finish times for each one. 

I understand that manhours must be recorded against each task but my question was more related to setting original durations when creating a schedule. For example should I use 1.25 days original duration with 10 budgeted manhours or should I round to 1 days duration with 10 budgeted man hours in order to keep the schedule start and finish times uniform? 

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Thu, 2018-11-01 17:31
#12
Rafael Davila
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Activity durations shall represent reality, if it takes 10 hours to execute then it is 10 hours, nothing more, nothing less.  There is no excuse for the scheduler not to take control of activity start time of day.  If an activity scheduled to take 8 hours took 10 hours it shall be scheduled and reported as such. When rounding durations resource costs might be pulled wrong ...

Tame-Activity-Start-Hour

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Thu, 2018-11-01 15:46
#13
Anoon Iimos
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Oh, well then you have to store the actual data (actuals cannot be changed). I presumed you have a baseline schedule compared against your current or actual schedule. Just make the changes on your current schedule starting from 50% complete and run the new schedule from there. For example: On your current schedule, set the data date exactly on where you reach 50%, everything on the left of the data date are actuals (you don't touch or change anything on it). On the right of the data date is where you apply all your fixes. Remember, do not run the schedule or change the data date until you have fixed everything. This would not be easy as for sure there are activities that have actually started on the left of the data date, but still spanning on the right or beyond the data date (take note of these activities). This is all for now as I'm running out of battery.
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Thu, 2018-11-01 15:14
#14
A T
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The project is around 50% complete but the calendars have been set up incorrectly and start and finish times have not been used meaning a large number of activities that have 1 days duration run across two days for example. 

Is there a way for me to fix the calendar and the start and finish time of each activity or would I have to start the schedule again and create a new one?

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Thu, 2018-11-01 15:10
#15
Anoon Iimos
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Sorry, but I don't understand what you mean by 50% complete or correct schedule. If 50% is in error, then you must consider scrapping the existing schedule and create a completely new one. Errors, maybe in calendars, logic links, and if resource loaded, then there's no easy fix.
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Thu, 2018-11-01 14:48
#16
A T
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Thank you for your response Anoon. I have a much better understanding.

My next question is regarding a project I have just started working on. I have taken over a schedule which is around 50% complete and the calendars have been set up incorrectly, as well as the start and finish times not being used correctly when progressing the schedule. Partial days are present throughout the schedule and I would like to tidy it up to put every activity to a whole day with the correct start and finish times

Is there an easy way for me to correct these issues with the schedule being half way through? 

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Thu, 2018-11-01 14:19
#17
Anoon Iimos
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You just need to be consistent. If you started counting in hours, then count everything in hours. However, it's normal to use Days (whole day or whole number) as Duration, simply because it is easy to understand when you are trying to communicate. Needless to say that the Schedule is one of the management tools. So for example: You were asked for the estimated duration of a certain activity? You don't give an answer that this activity can be finished in xyz hours and xxx minutes, using zxz number of men and equipment, but instead you would say (by looking at the huge calendar on the wall): If we are able to start today, then probably we can finish the activity by end of Monday next week, which is around five days, provided with necessary crew and equipment. Again, your answer might be in error as you did not elaborate that you have considered Sunday as non-working day.
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Thu, 2018-11-01 12:56
#18
A T
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Thank you for your reply Zoltan. I presumed that would be the case. 

What I'm trying to understand is will this not affect the overall duration? 

For example if you have 20 activities and the duration estimates are as follows

10 activities x 1 day 

10 acivities x 1.5 days

All following in sequence the duration would be

10 + (10*1.5) = 25 days duration 

If i round these durations to 2 days then the overall duration will be 10 + (10*2) = 30 days 

This gives an extra 5 days overall. 

I know this is a basic example but I'm just trying to understand how rounding up and down to whole numbers works when estimating durations.

Thanks

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Thu, 2018-11-01 12:14
#19
Zoltan Palffy
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yes if not then the times will be off. In the background P6 schedules using times which are setup in the calendars 

for example activities A to B to C

Activity A is 1.5 days 

Activity B is 1 day 

Actvitiy C is 1 day

Actviity A is scheduled to start on day #1 at 8:00 am and since it is 1.5 days duration it finishes on day #2 at 12:00 noon

thsi means that activity B can begin on day #2 at 12:00 noon and since it is 1 day duraiton it will finish on day 3 at 12:00 noon

This means that a 1 day activity has actually spanned 2 days and wil show starting on day #2 and finishing on days #3 when it should really start and finish on the same day it is ONLY 1 day.   

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