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International Gin & Tonic Day!
October 19, 2017
There seems to be two International Gin and Tonic days – one on April 9th and another on October 19th.
Some links of possible interest:
Here’s To Your Health! It’s International Gin & Tonic Day at laist
International Gin & Tonic Day: Celebrate With Tasty Cocktail at Hamptons.com
Wikipedia: Gin and tonic