snippet.clj

(require '[java-time :as t])

(defn at [t {:keys [hours minutes seconds]}]
  (let [m (t/as-map t)]
    (cond-> t
      hours (t/plus (t/hours (- hours (:hour-of-day m))))
      minutes (t/plus (t/minutes (- minutes (:minute-of-hour m))))
      seconds (t/plus (t/seconds (- seconds (:second-of-minute m)))))))

(defn next-working-day [t]
  (let [{:keys [day-of-week]} (t/as-map t)
        delta-day (if (>= day-of-week 5)
                    (- 8 day-of-week)
                    1)]

    (-> t
        (t/plus (t/days delta-day))
        (at {:hours 9}))))