function interval(then, now) {
let t = now;
let mois = d3.timeMonth.count(then, now)
if ((t = d3.timeMonth.offset(t, -mois)) < then) t = d3.timeMonth.offset(t, -1), mois;
let jours = d3.timeDay.count(t, then);
if ((t = d3.timeDay.offset(t, jours)) < then) t = d3.timeDay.offset(t, 1), jours;
let heures = d3.timeHour.count(t, then);
if ((t = d3.timeHour.offset(t, heures)) < then) t = d3.timeHour.offset(t, 1), heures;
let minutes = d3.timeMinute.count(t, then);
if ((t = d3.timeMinute.offset(t, minutes)) < then) t = d3.timeMinute.offset(t, 1), minutes;
let secondes = d3.timeSecond.count(t, then);
if ((t = d3.timeSecond.offset(t, secondes)) < then) t = d3.timeSecond.offset(t, 1), secondes;
return {mois, jours, heures, minutes, secondes};
}