How it works (my idea), you open the jar, let's say on the first of September,I Check the label, it says "Once opened keep refrigerated and use within two weeks", so I take a pen and write "14/09/14" on it,,, simples innit...
http://www.bbc.co.uk/news/uk-scotland-scotland-business-29741564
http://www.bbc.co.uk/news/uk-scotland-scotland-business-29741564