Winter Ferry Bookings to Iceland Explained

why can't I find winter booking system for ferry to Iceland if it runs year round?

Norröna Sailing Schedule

Norröna offers weekly departures from Hirtshals to Seyðisfjörður (Iceland) from mid-March to late November, with a weekly return trip during the same period. Additionally, there are weekly sailings between Iceland and the Faroe Islands from mid-March to late November. For the Faroe Islands to Denmark route, there are weekly departures year-round, with twice-weekly sailings during the summer.