Convert set to list:
set.stream().collect(Collectors.toList());

Convert a set to ArrayList
set.stream().collect(Collectors.toCollection(ArrayList::new));

Construire un Instant en UTC
GregorianCalendar date = new GregorianCalendar(annee, mois, jour, heure, minutes);
date.setTimeZone(TimeZone.getTimeZone("UTC"));
dateFin.toInstant();

Annee d'un Instant
LocalDateTime.ofInstant(instant, ZoneOffset.UTC).getYear();