Different Periods on Each Side
Why supply and demand are measured over different windows, the three mismatches that follow, and how to align them without forcing everybody onto one calendar.
Supply is usually measured over a financial period: a quarter, a month, a year. Demand arrives in project phases, sprints, contract terms and regulatory deadlines, none of which align with the financial calendar or with each other.
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The subtraction requires one period. Choosing it, and converting everything into it, is the second half of making the two sides comparable.
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The three mismatches
A claim that spans the boundary: half of it lands in this quarter and half in the next, and both plans count all of it.
A claim shorter than the period: two weeks of work inside a quarter appears as a small fraction and hides the fact that it must happen in specific weeks. And a claim with no period at all, which is the standing commitment.
The boundary claim
The most common and the most expensive. A project running from February to May appears in two quarterly plans, and unless somebody splits it, both carry the whole figure.
Splitting by calendar time is the default and is often wrong — effort is rarely even — but it is better than not splitting, and stating the split makes it correctable.
The short claim inside a long period
Two weeks of work in a thirteen-week quarter is 7.7 per cent of a quarterly plan and a hundred per cent of the fortnight it actually occupies.
Quarterly planning cannot see that, which is why quarterly plans say there is capacity and monthly reality says there is not. Where the work is lumpy, the plan has to be monthly even if the governance is quarterly.
Choosing the planning period
Short enough to show the lumps, long enough that the overhead is tolerable. For most knowledge work that is a month; for operations with daily variation it is a week; for construction-like work with long tasks it can be a quarter.
The test is whether a complete claim typically fits inside one period. If most claims span several, the period is too short; if several fit inside one, it is too long.
Two periods, deliberately
The usable arrangement in most organisations: a quarterly account for governance and a monthly account for allocation, with the quarterly being the sum of three monthlies rather than an independent document.
Independent quarterly and monthly plans will disagree, and the disagreement will be discovered by somebody senior at the worst possible moment.
The rolling horizon
Capacity further out is less certain, and plans that extend twelve months at the same granularity as next month are pretending otherwise.
A rolling horizon — detailed for one period, outline for three, indicative beyond — matches the certainty actually available and stops the plan being wrong in a way that discredits the near-term part.
Aligning without forcing
Nobody should be made to change their natural period. Sprints stay sprints, contracts stay contractual, regulatory deadlines stay where they are.
The account converts, as it does with units: each claim is expressed in the planning period with its own dates recorded beside it, so the original is recoverable.
The year-end effect
Financial year ends distort both sides: budgets are spent, leave is taken, commitments are rushed to close. A plan built on an average period will be wrong in the final one, predictably.
Carrying a year-end adjustment in the account, with a note saying what it is for, is more honest than discovering it every year and treating it as a surprise.
Recording the period on every figure
Every number in a capacity account carries its period: 2,061 hours is meaningless without "this quarter", and "1.5 FTE" is meaningless without the window.
That sounds obvious and is routinely omitted in exactly the documents where it matters, which are the summary slides that leave the planner's hands.
The four dates every claim needs
- Earliest start, which is often not the same as desired start.
- Desired start, which is what the claimant said.
- End, firm or guessed.
- The date the claim itself expires if unconfirmed.
Four dates, and the first is the one nobody records. A claim that cannot start before April does not compete for February capacity, and without that field the plan assumes it does.
The period mismatch that looks like a shortfall
A quarterly account showing adequate capacity and a team visibly drowning in week six is almost always a period problem rather than a quantity problem.
Before escalating a shortfall, split the period into months and look again. In a good proportion of cases the total is right and the shape is wrong, and the remedy is sequencing rather than resourcing.
What to align first
The book and the supply figure, to the same window, before anything else. Aligning either of them with the financial calendar is secondary, and aligning the organisation's governance cycle with reality is a much longer conversation that does not have to be won first.