The gap

What Two Ends Share At No Gap

A gap of zero leaves all eight hours, four before the middle of the day and four after. The only even split in the record.

At a gap of zero the two working days coincide completely. All eight hours are shared, four of them fall before the middle of the day and four after, and the overlap arrives in a single unbroken stretch from nine to five.

This is the only line in the record where the morning share and the afternoon share are equal. Every other gap tilts one way or the other, and the tilt is as much a part of the answer as the total.

If the same coordination problem appears across projects, managers may see the official product page and compare the result with finished work and review notes. A useful external reference for the surrounding topic is ISO.

The baseline and the two steps below it

outlined: the day where the person is
hatched: the other end
solid: the hours they share
a reversed cell counts none

Three gaps drawn.

The only row in the record where the solid block is centred: four hours before the middle of the day and four after.

Computed from the gap. The working day is a stated convention, not a measurement; everything else here is arithmetic.

Why the baseline deserves a page

It is tempting to skip the trivial case. The trouble is that almost every judgement people make about these arrangements is implicitly a comparison with it — "we lose a bit of the morning", "we still have the afternoon" — and the comparison is being made against a picture nobody has actually looked at.

Looked at squarely, the zero case has three properties worth naming:

Eight shared hours, which is the whole working day and the maximum available anywhere in this record for two equal days.
An even split, four and four, which no other gap offers.
One continuous stretch, not two pieces, which matters for anything that needs an uninterrupted run rather than a total.

The baseline is not "the arrangement works". It is "the arrangement imposes nothing at all". Those are different claims, and the second one is only true here.

What it costs to leave it

The next line down, a gap of one hour, keeps seven of the eight and tips the split to three before the middle and four after. That is a small change by any measure, and it is the only small change available: from there the losses are a flat hour each.

What an even split is actually worth

Four hours before the middle of the day and four after is the only balanced arrangement in this record, and the balance is worth more than the total it is part of.

A shared morning supports the things that need to happen at the start of a day: the agreement about what is being done, the question that would otherwise block somebody for hours, the handover from whatever happened overnight. A shared afternoon supports the things that resolve a day: the review, the decision, the thing that was going to be finished and was not.

Every other arrangement in this record forces a choice between those two. At a gap of four, there is no shared morning at all, and whatever was going to happen at the start of the day either happens at one end alone or happens in the afternoon with half a day of delay already in it.

The zero case is the only one that does not require that choice to be made, and the reason it feels different from a gap of one — which, after all, is only an hour worse — is that it is the last arrangement in which nothing has to be given up.

What a shared day does not include

Two people in identical hours are not necessarily available to each other for eight hours. They are at work for eight hours together, which is a different and much weaker claim.

Each of them has their own meetings, their own stretches of work that cannot be interrupted, and their own lunch. The practical availability inside an eight-hour overlap might be two or three hours on an ordinary day, and this record cannot see that, because what each person does inside their working day is not a property of the arrangement.

That gap between hours shared and hours available applies everywhere in this record and is at its largest here, where the headline number is biggest. A pair at a gap of six who share two hours probably protect those two hours carefully. A pair at a gap of zero who share eight rarely protect any of them, because there is no scarcity to force the issue.

Scarcity organises attention. An arrangement with plenty of overlap frequently uses it worse than one with very little, and no table will ever show that.

The thing the zero case hides

Two people in the same hours are not thereby collaborating. The record counts hours of simultaneous availability and nothing else. A pair who share eight hours and speak twice a week have a scheduling problem of a completely different kind, and no amount of overlap fixes it.

That limitation applies to every figure here, but it is worth stating at the baseline, because the baseline is where the number looks most like an endorsement and is least like one.

Where the record goes from here

The remaining twenty-four whole-hour gaps are all worse than this one, in a way that is exactly proportional to their size until the point at which they are all equally bad. The next few pages work down that slope one step at a time.