Learn · Scheduling 101
Why five working days is not always five days on the calendar
After this subject you can say what a work calendar is, tell a working day from a day on the wall chart, and explain why the same five days of work can land on two different dates.
Five days on the wall, seven on the schedule
You give a piece of work five days and it starts on a Thursday. You count five squares across the wall chart and land on Monday. The schedule says Wednesday. Nobody has made a mistake — the two of you are counting different days, and this lesson is which days each of you means.
The days your job turns up
A calendar is the working time a job keeps: which days it works, and which days it does not. Most jobs are on five days a week. Some pours run six. A shutdown week belongs to nobody. Between your five squares and the schedule's Wednesday sit three things: where the work starts, how long it takes, and the calendar it is on.
Why it matters — a job usually keeps one and some of the work keeps its own, because a cure carries on through a Sunday whether anyone is on site or not.
So a day is not always a day
A working day is a day the calendar makes available to work. Where five of them land depends on where you start counting and on which days the calendar gives you. On an ordinary five-day week, begin on a Thursday and five of them reach the following Wednesday, because the two in between are not yours to spend.
Why it matters — the start date is doing as much of the arithmetic here as the calendar is.
And the days it does not
A non-working day is one the calendar does not count: a weekend, a holiday, a planned shutdown. Work on that calendar does not spend those days, so the schedule does not either. That is why five days of work starting on a Thursday finishes on Monday where the job works seven days, and on Wednesday where it works five.
What that does to a finish
Add a working day to a piece of work and the finish does not always move by one date. On a five-day week, a Friday finish moves to the Monday — three dates later. The grid says the basis in four words: duration in working days. Given a start and a duration, the finish is that duration walking the project calendar.
Why it matters — this is why two people with the same number in front of them can read two different finishes.
The question to ask before arguing about a date
Ask
Which calendar is this piece of work on?
Instead of
How many days is it, roughly?
Ask
Does this crew work Saturdays?
Instead of
Can we squeeze it in by Friday?
Ask
Which weeks does this job not work at all?
Instead of
We will make it up over the holidays.
What to remember
- A calendar is the working time a job keeps — which days it works and which it does not.
- A working day is a day the calendar makes available; where five of them land depends on where you start.
- A non-working day is one the calendar does not count, so work on that calendar does not spend it.
- Five working days starting on a Thursday span five dates on a seven-day job and seven on a five-day one.
- Given a start and a duration, the finish is that duration walking the project calendar.
Check which days your job works before you argue about a date
Open a project and look at the calendar it is running on: the days it works, and the weeks it does not. Then take one piece of work you were sure was five days and read where the schedule lands it. If the two answers differ, the start date and the calendar are where to look. Bring your own job calendar to a demo if you would rather walk through it with somebody.