sleep-setpoint-calculator.js

const dayOfMonth = d => `${d.getDate()}/${d.getMonth()}/${d.getFullYear()}`;

const midnightDistance = d => Math.abs(realMidnightDistance(d));
const realMidnightDistance = d => (d.getHours() - 12) > 0 ? -midnightDistancePM(d) : midnightDistanceAM(d);
const midnightDistanceAM = d => (d.getHours() * 60) + d.getMinutes();
const midnightDistancePM = d => ((24 - d.getHours()) * 60) - (60 - d.getMinutes());

const excludeDistLessThan = threshold => d => realMidnightDistance(d) > threshold; 

const closestToMidnight = d => 
    d.length === 1 ? d : d.reduce(
        (closest, value, index) =>
            midnightDistance(value) >= closest.dist
            ? closest
            : { value: value, dist: midnightDistance(value) },
        { value: 0, dist: Infinity } // default
    ).value;

const earlierSleepTime = d => 
    d.length <= 1 ? d : d.reduce(
        (closest, value, index) =>
            realMidnightDistance(value) >= closest.dist
            ? closest
            : { value: value, dist: realMidnightDistance(value) },
        { value: 0, dist: Infinity } // default
    ).value;

// use calculateAverageFrom(30) to get the average from 30 days ago
function calculateAverageFrom(days) {
    const partial = _.chain(sleep)
        .map(s => new Date(s))
        .groupBy(dayOfMonth)
        .values()
        .value();
    
    return _.chain(partial)
        .slice(partial.length - days)
        .map(d => d.filter(excludeDistLessThan(-300))) // remove nap
        // .flatMap(closestToMidnight)
        .map(earlierSleepTime)
        .flatten()
        .map(realMidnightDistance)
        .mean()                     // distância média de meia noite
        .value();
}

given a sleep variable, which is an array of all your sleep-time start, in unix time, use calculateAverageFrom(30) to get the average from 30 days ago. The result is the distance (in minutes) from midnight. Negative values indicate distance before midnight (e.g.: -120 indicate that your setpoint is 10pm). Positive values indicate distance after midnight (120 indicates 2am).