First Saturday of February every year
Swedish National Day of Running. Celebrating this day is easy for most people: simply put on your running shoes, appropriate training clothes and something to be noticed in the dark (it gets dark early this time of the year), then go outside to run. Another option would be to join one of your local running events.
The idea for this day occurred to one of the writers of the Swedish edition of Runners World, who gathers a crowd in central Stockholm on the first Saturday of February. Get inspiration for your own celebration or join them through Facebook at Löpningens Dag.
In the U.S. we can celebrate by intensely watching ESPN or training for the U.S. National Running Day, which is the first Wednesday of June every year—this year it's June 4 (which allows two full days to recuperate before Sweden's National Day on June 6).