Denmark, Iceland and Norway celebrate today, Whit Monday, as a national public holiday.
Whit Monday is the day after Whitsun (Whit Sunday or Pentecost). In Christianity, Pentecost commemorates when the Holy Spirit descended from heaven upon the disciples following Jesus’s ascension; which was celebrated a couple of weeks ago, also as a public holiday.
Pentecost is the last day of Easter and happens 50 days after Easter Sunday — hence the ‘pente’, from the Ancient Greek.
Whit Monday is a moveable holiday, as is Easter. It used to be a day off in many European countries, but was gradually replaced by fixed secular dates.
In Iceland this is a three-day working week; because the country will celebrate its independence day this Friday.