The day was first celebrated in 1996, after it was proclaimed that year by then Governor General of Canada Roméo LeBlanc, to be celebrated on June 21 annually. (wikepedia)
June 21 is also known as the summer solstice and the longest day of the year.
Most provincial jurisdictions, however, do not recognise it as a statutory holiday.
Happy National Aboriginal Day. If you get an opportunity today, do something to honour your culture and heritage!
If you want to learn more about aboriginal culture, look for activities within your community, particularly the friendship centres.