I gather from CharonQC and Blawg Review that April 6 is Tartan Day in North America and is celebrated by Canadians and Americans of Scottish heritage. Craig Williams (also of Welsh ancestry) of May it Please the Court is going to feature this in his blawg review. At the time of writing this, it is only just April 6 in the USA, so we have to wait.
Some of those of us of Scottish descent in the UK actually believe that the idea of clan tartans was a Victorian invention. But obviously a well-advertised one.
Tartan Day was conceived in Canada in about 1986 and has been celebrated in the USA since 1998, so obviously after my time.