Circadian Planner

What it will measure

Nothing, in the strict sense. The planner will not measure your circadian phase — that requires assays this site has no access to. It will estimate a plausible position for your internal clock from the timing you report, and then arrange the controllable parts of your day around that estimate.

The distinction matters, and the tool will keep making it. An estimate built from your own reported wake times is a reasonable planning assumption. It is not a measurement, and it will never be presented as one.

What it will ask you for

• Your usual wake time, and how much it varies across a week.
• The hours you need to be working or available.
• Roughly where you are, so daylight timing can be approximated.
• How much daylight your mornings realistically contain — not how much you would like them to.
• When you drink caffeine and when you exercise.
• What your evenings are actually committed to.

It needs an honest picture of an ordinary week, not an ideal one. A plan built on the week you wish you had will fail in the first three days.

What it will give back

A seven-day schedule marking four things per day: when the sleep opportunity opens and closes, when to prioritise getting light, when to bring the light level down, and — if you are moving your timing rather than holding it — where the next incremental step sits.

Shifts will be staged rather than jumped. Where the plan asks you to move, it will show the intermediate days rather than only the destination.

The assumptions it will rest on

These are the load-bearing ones, stated so you can judge whether they hold for you.

1. Your reported wake time approximates your clock’s morning. For most people on a settled schedule this is reasonable. For someone whose schedule has recently changed, or who wakes by alarm far earlier than they otherwise would, it is weaker.
2. Light is the dominant timing signal. The plan prioritises light over meal timing and exercise timing, because the mechanism is better described.
3. Gradual shifts are more sustainable than abrupt ones. This is a practical assumption as much as a physiological one — plans people can follow beat plans they abandon.
4. You are on a day-oriented schedule. If you are not, the Shift-Work Planner is the right tool; this one’s assumptions will not hold.

Where the method is still being specified

The step size for a staged shift is not settled. How far to move per day depends on direction, on individual variation, and on how much light the plan can actually count on, and we will not publish a figure before the sources supporting it are attached.

The same applies to the width of the recommended light window. The direction of the advice is well founded; the specific duration is not something this page will assert yet.

Until those are fixed, read the staging as “move in small steps, and give each step a few days” rather than as a precise schedule.

What it will not do

• It will not diagnose. No output will state or imply that you have a circadian rhythm sleep–wake disorder, delayed or advanced sleep phase, or any other condition.
• It will not give medication or supplement guidance of any kind.
• It will not tell you how many hours you should sleep.
• It will not score your schedule or rank you against a population.

Limitations

It cannot see how bright your mornings actually are, how well you slept last night, or whether your late evenings are a choice or an obligation. It infers everything from what you type, and the inference is only as good as the input.

It also cannot tell you whether timing is your problem at all. A schedule that looks sensible on paper and still does not work is genuinely useful information — and it is a reason to speak to someone, not a reason to re-run the planner with different numbers.