[рони]

shkarol,

const formatter = new Intl.DateTimeFormat("ru", {
            hour: "numeric",
            minute: "2-digit"
        });

        const sleepTime = (str, back) => {
            let [h, m] = str.split(":");
            let time = new Date();
            let arr = [];
            let duration = back ? -90 : 90;
            for (let i = 1; i < 7; i++) {
                time.setHours(h, (+m + duration * i), 0, 0);
                arr.push(formatter.format(time))
            }
            return back ? arr.reverse() : arr;
        }
        console.log(sleepTime('7:30', true));
        console.log(sleepTime('23:40'));