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"Must Start on Particular Day" Constraint

4 replies [Last post]
Tony McClennon
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Joined: 19 Nov 2002
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I'm trying to find a way of getting a 5 day task to start on the first working day of a week, regardless of the day it's predecessor finishes. For example, Task A finishes on a Thursday, then I want task B to start on the Monday, not the Friday.

I know I could put a lag in the link, but this only works until I update the schedule and task A may move.

I have also considered setting up a calandar that shows Monday only as a work day, then adding in a milestone with this calendar, which in turn drives task B which would do the job. However, it would be neater if i could add a "Must start on a Monday" type constraint, and was wondering if anyone has done this previously.

Many thanks.


Tony McClennon
User offline. Last seen 23 weeks 2 days ago. Offline
Joined: 19 Nov 2002
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Thanks for the replies. I did end up setting up a calendar with Sat/Sun working, against which a predecessor task for "travel to site" is set up, which then links into the actual task (Mon-Fri working calendar) thus making sure it starts on a Monday.

Rafael Davila
User offline. Last seen 1 week 2 days ago. Offline
Joined: 1 Mar 2004
Posts: 5230

Prefer to use lag calendars, no extra tasks/activities to update or hide. Just create a lag calendar working only on Sunday and use this calendar on your links with a lag of 1 hr.


Note that only link from activity 2 to activity 3 and activity 3 are the critical path. Activities 1 and 2 although on the longest path (easy there is just one) are not critical, longest path is not critical all the way, and this is due to pure logic, under resource leveling it gets more complicated.

A similar approach can be used when some activities must start on the week end but once started can continue during the regular week. To me the everyday use of different lag calendar occurs with concrete curing.

Sorry I do not use MSP but hope the idea on using lag calendar to control successor task is of help.

Evgeny Z.
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Joined: 13 Jan 2008
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There is actually a quite elegant way to do this in MS Project

Create a separate calendar “MondayEarlyMorning”, with working time every Monday 00:00 – 01:00, all other times are not working.

Then, before every task, which you want to start on Monday, you should insert another task “MondayStartMilestone”. This task should have duration <=1h  and should have a calendar “MondayEarlyMorning”, assigned to it. As a consequence, the task, which will be linked to it will always start on Monday.


I think that milestone on Mondays is the best possible solution.