From
The Facebook page:

“ International Gin and Tonic Day was founded in honour of Mary Edith Keyburn, a remarkable woman who loved to have the occasional tipple of gin and tonic. Edith passed away on October 19th, 2010 - at the age of 95 - in hospital with a gin and tonic at her side. It was smuggled into the hospital in a water bottle and served in a teacup. We hope that you'll have a tiipple on October 19th and that we can all make as gracious an exit from this life as Edith did.”