Black Tot Day: The last day of the officially sanctioned rum ration in the Royal Navy.

Black Tot Day was the last day on which the Royal Navy issued sailors with a daily rum ration.

Rum is a liquor made by fermenting and then distilling sugarcane molasses or sugarcane juice. The distillate, a clear liquid, is often aged in barrels of oak. Rum originated in the Caribbean in the 17th century, but today it is produced in nearly every major sugar-producing region of the world.

The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against France. The modern Royal Navy traces its origins to the English Navy of the early 16th century; the oldest of the UK's armed services, it is consequently known as the Senior Service.

July 31 is the 212th day of the year in the Gregorian calendar; 153 days remain until the end of the year.