Traditionally the last person still sleeping in the house is dubbed the "sleepyhead" and awakened with water, either by being thrown into a lake or the sea, or by having water thrown on them.
In the city of Naantali, a celebrity is chosen every year to be the Sleepyhead and thrown into the sea for a somewhat rude awakening to start the day.
The origin of Sleepyhead Day is to be found in the legend of the Saints of Ephesus who slept in a cave for 200 years hiding from persecution by the Roman Emperor Decius.
Sleepyhead Day has been observed in Finland since the Middle Ages and the first written record is from a hymnal calendar of 1652 when it was celebrated on June 27th.
Since 1709 the day has been observed on July 27th.
Sleep disorders common
The Sleep Union, an umbrella organisation for groups working with sleep disorders, points to a more serious side to the day. It says that there are over 600,000 people in Finland who suffer from sleep disorders. Major causes are the fast pace of life, stress and unsuitable sleeping conditions.
The union is organising morning and afternoon events Monday at Helsinki's main railway station to focus attention on sleep disorders. It says that, for example, a lack of sleep is a major factor in road accidents, with fatigue accounting for close to one-fifth of all traffic accidents.