We've had internships in Canada for at least 100 years, in the medical field for example, but I think the time when we started to see the prevalence of unpaid internships was around the 2008 financial crisis. This is something that built in the United States and now has been growing in Canada and it was exacerbated by the lack of awareness about the laws that do exist.
On March 27th, 2014. See this statement in context.