The pattern, and the tool it deserves.

01 — The pattern

Envelope budgeting gives every amount a job. The way you run money asks one more thing of it: a home. The trip next year, the savings you will not touch for a decade — each sits somewhere matched to when you will need it. Cash for soon, a low-risk fund for later, shares for the long run. You did that on purpose, and it was the right call.

It cost you one thing: the single number. When everything sat in one account, the balance told you where you stood. Spread across accounts, it no longer does. Now an expense lands and you do the sums by hand — which account covers it, whether that money was promised to something else, whether paying it means selling at a bad moment.

So you keep the books yourself, in your head or in a spreadsheet beside your budgeting app: what each amount is for, against where it actually sits. Duration is that work, made into a proper tool.

02 — Two axes

In Duration, every amount carries two labels. The purpose says what it is for. The horizon says when you will need it — and the horizon decides where the money sits.

Money held this way moves on its own schedule: you decide on payday, and the cash follows when you transfer it. So Duration keeps two numbers where your old app kept one. Allocated is what you have decided. Funded is what the accounts actually hold.

The gap between them is drift — not an error, just the cash not yet caught up with the decision. Duration shows the drift at each horizon, and the one transfer that closes it.

A worked moment: 2,000 assigned to short-term on payday is still in the debit account. Short-term reads 2,000 under and out-of-pocket 2,000 over — one transfer closes both.

03 — What it is for

Returns are not the point.

Your money is invested, so it may well grow — but Duration takes no credit for that and holds no opinion about it. What the app gives back is legibility: a clear, current answer to what your money is for and where it sits. The benefit shows up as mistakes not made — a fund not sold into a dip because the cash was already planned for, a partner's share not quietly forgotten, a month-end that takes a calm half-hour instead of an afternoon.

The method is the same whether you look after a little or a lot. If the point were yield it would be pointless on a small balance — the surest sign the point was never yield. That is the whole of it: a clear view of money held with intent, at any scale.

04 — Stated plainly

• No optimiser

  Duration records your decisions and shows you their consequences. It will not move your money for you, or tell you that now is the moment to act.

• Friction on purpose

  Deciding where money goes is the one part worth doing by hand — it is where the judgement lives. The tool is here to inform that, not to automate it away.

• A desk, not a phone

  Reviewing, reconciling and allocating are sit-down work, not taps on the move. Duration is a web app, made for the desk.