Computing tasks Finish date in Project

Copper Contributor



I've unexpectedly run into the following situation: for a project, I've set the work schedule for 4hours / day and entered a task with the duration of 40hours, which I've computed as 10 working days of 4 hours, expecting to find an interval of around two weeks (5 working days / week). Yet, the result was different, the period being shorter (around one week). It might be something very obvious but I do not see the reason. Could you help me please?


I do not understand how finish dates of tasks T1 and T2, auto-scheduled, marked in yellow, are computed (for 4 working hours per day). T1 and T2 are set 'As soon as possible' with no predecessors and the Project start date is the one displayed 


I've tried to upload the Project file but it seems it is not supported, so here is a screenshot of the project in Task Usage and one of the Schedule Options 


Thank you very much!

7 Replies


Not quite enough information but let's see if I can give you some guidance. First of all, go to File > Options > General group and select a Date Format that includes the time.


Did you create a custom project calendar that limits working days to 4 hours, from 3 to 7? It should look like this:


You set the scheduling options for start and end times and defined a "day" as 4 hours. But, you must also set the Project start time as shown and the Project Calendar as shown here:



Doing this should give you a Task Usage view that looks like this:


Hope this helps.




@John-project Thank you very much for your message and recommendations!


I'll follow your recommendations!


I haven't created a 4h calendar because for the other tasks it takes into consideration 4h working days. But indeed I've thought about trying to do so and on the 'troublesome' tasks T1 and T2 I've started to change the calendar but finally left the Standard one. I've thought this could be the reason for considering 8h days for those tasks. I've tried then to delete any specific calendars on those tasks and set the Calendar to None as it appeared for the other tasks but this didn't work and I didn't see any other specific way of reseting the calendar for those tasks.


If I hadn't tried to set any specific calendar on those tasks, I think it would have taken into consideration 4h working days, as for the others. Anyhow, I think it would be helpful to be able to reset the calendar to the implicit settings for specific tasks in order to solve easily such situations.


Thank you very much for your reply and recommendations!


best response confirmed by Alina_Andreica (Copper Contributor)
You need to have a custom 4h workday calendar. If it only applies to those two tasks, then use the Task Calendar field to set the 4h workday calendar for those tasks and leave the Standard calendar as your Project calendar.

Also, if the 4h workday is limited to certain tasks, do NOT change the definition of a "day" to 4 hours, leave it at the default 8h or whatever a standard day is for the rest of the tasks. Project only allows one definition of a "day" so if you have a mixed bag, I suggest you either stick with entering duration values in hours (that works for everything), or only used days in the duration field for non-4h day tasks. The 4h workday task duration will still need to entered in hours.

Understand that Project calculates all time values to the nearest minute regardless of the setting you use for duration.



Sorry for bothering again, I've created and applied a 4h calendar for all tasks and now the number of weeks has doubled compared to what I have computed, I do not understand why :cool:


The calendar has 4h in the working days and Saturday and Sunday non-working 


Thank you very much,



Say what? Let's start over.
1. Do you or do you not need 4h workdays for Monday through Friday for ALL your tasks?
2. What is your Project Calendar?
3. What is the Base Calendar for resource W4?
4. Do your resources have workdays that are different from the Project calendar?
5. What is the task type for T1 and T2 (i.e. fixed units, fixed work, or fixed duration)?
5. On tasks T1 and T2 what is the assignment level of the W4 resource?



Thank you very much! 


The project calendar was set as well to 4h but the calendar for the working resources remained Standard, therefore from the intersection with the 4h one, remained only 15-17, therefore 2h / day


Actually, I've logically deduced that from some standard specification, maybe only 2 working hours remained - and I've even thought to change the interval 15-19h to a one included in the standard working time - but didn't check the resources calendar until you recommended:lol: 


It's ok now, thank you very much!


With all best wishes,



What you are doing makes no sense to me but if it works for you, that's good.