So why is Tartan Day celebrated on the 6 April each year? Because the Declaration of Arbroath was signed on the 6 April 1320:

'As long as but a hundred of us remain alive, never will we on any conditions be brought under English rule. It is in truth not for glory, nor riches, nor honours, that we are fighting, but for freedom - for that alone, which no honest man gives up but with life itself.'

This is a translation of part of the Declaration of Arbroath, foremost among Scotland's state papers and perhaps the most famous historical record held by the National Records of Scotland (NRS). The Declaration is a letter from the barons and whole community of the kingdom of Scotland to the pope in 1320, asking him to recognize Scotland's independence and acknowledge Robert the Bruce as the country's lawful king.

The Declaration was in Latin and was sealed by eight earls and about forty barons. Over the centuries various copies and translations have been made, including a recent microscopic edition.

You can visit the National Records of Scotland website to view an image of the original declaration, use 'zoomify' to see the detail of the text and seals, and read a transcript or translation of the document.

More information:

http://en.wikipedia.org/wiki/Tartan_day