According to Wikipedia:
Ben & Jerry’s Free Cone Day is an annual event, held in late April or early May, in which Ben & Jerry’s scoop shops give out free ice cream cones all day. Over one million free cones are given away each year. Charitable organizations are often present at the stores each year and enjoy a significant amount of fundraising success.
The first Free Cone Day was held on May 5, 1979. It was done by Ben and Jerry as a customer and staff appreciation event for the one year anniversary of their ice cream store’s opening, and has continued ever since.
The 28th annual Free Cone Day was held on the day of April 25, 2006.
The 29th annual Free Cone day will be April 17, 2007.
Here are Ben & Jerry’s store locations in Canada