Still an autonomous Grand Duchy of the Russian Empire in early December 1917, Finland had its own Parliament and a Senate which acted as a government.
On December 4th, Senate Chairman Pehr Evind Svinhufvud, in effect the country's Prime Minister, presented Parliament with a proposal for Finland to be declared an independent republic.
Two days later, on December 6th, Parliament adopted the declaration.
Monday's gathering marking the event is being held in the same chamber where the Senate met 100 years ago, which is now used for weekly cabinet meetings with the President.
In addition to cabinet ministers, this special session is being attended by descendants of the members of the 1917 Senate, and a group of upper secondary school students from Kuopio.
Earlier this year, a national school project was launched asking pupils to draft a new "declaration of independence", laying out a vision of the next one hundred years for Finland and its people.
The work of the four students attending Monday's session was judged as the best vision of that future.