NeuroSync — your day, laid out against the hours you sleep

You tell it when you go to bed and when you get up. From those two numbers it works out where you are in the day right now, when to go outside for daylight, when to start dimming the lights, and roughly when the things you do all day tend to land best. That is the whole app.

It is for anyone whose schedule has drifted — a new shift pattern, a move across time zones, a newborn — and who wants the day arranged around sleep instead of guessed at. There is no account and no sign-up; the schedule and the nights you record stay in your browser's local storage and never leave the device.

The four screens

• Dashboard — a clock showing which stretch of your schedule you are in and how far through it you are, beside the modelled cortisol and melatonin curves. The curves are drawn without a vertical scale on purpose: a number next to the word "cortisol" reads as a lab result, and this is not one.
• Light — when to get outside in the morning and when to dim the lights in the evening, both shifted to your own schedule.
• Sleep — set your bedtime and wake time, and record nights yourself. Averages and any shortfall against your target are computed only from nights you actually entered, and the log starts empty.
• Activities — eight generic slots (focused work, morning exercise, open-ended thinking, meetings, a break, strength training, reading, dimming the lights) placed relative to your wake time. Rules of thumb about time of day, not advice about you.

Where the curve shapes come from

The model is anchored to timings reported in the literature, kept in one place in the source so they can be checked: cortisol peaks about 30 minutes after waking and bottoms out in the first half of the night; melatonin onset (DLMO) is about two hours before habitual bedtime, its peak about an hour before the core-temperature minimum, which itself sits around two hours before waking.

Individual timing varies widely. These are population averages, not predictions about any one person, and the curves will look the same whatever you actually did today.