What is the difference between white and dark rum?

Little: the European regulation allows rum to be coloured with caramel and sets no ageing requirement, so a dark rum need not be older than a light one.

Annex I to Regulation (EU) 2019/787 contains exactly one rule on colour for rum: only caramel may be added as a means of adjusting the colour. It says nothing about how long rum must spend in cask. By comparison, for whisky the same annex requires at least three years of maturation in wooden casks not exceeding 700 litres. So with rum you do not have that certainty, unless the bottle or its origin tells you more.

Molasses is what is left over from making cane sugar; sugar cane juice is the juice of freshly pressed cane. The regulation allows both within the same rum category.

The description in Annex I is literal: rum is produced by distillation of the product obtained by alcoholic fermentation of either the molasses or syrup produced in the manufacture of cane sugar, or of sugar cane juice itself. Rum based on juice is called rhum agricole in French. In Martinique this raw material is even mandatory: the AOC Rhum de la Martinique, recognised in 1996, only permits rum from fresh cane juice.

A pot still distils in separate batches; a column still works continuously and can distil to just below the legal limit of 96 per cent.

That limit is in the regulation: rum must be distilled to less than 96 per cent alcohol. The closer a distiller gets to that limit, the less of the original raw material ends up in the distillate. Both methods produce rum that meets the same category, and both can end up white or dark in the bottle. The still therefore says more about a rum's character than its colour does.

Under European rules, not a single year: the rum category has no minimum ageing period. What does exist are national rules in the producing countries.

In Martinique, the French institute INAO sets out what may be called rhum vieux: at least three years in oak casks and bottled on the island. Rum that has spent at least twelve months in cask is called rhum élevé sous bois there. Other producing countries have their own rules. If there is an age on the label, check where the bottle comes from, because the same number does not mean the same thing everywhere.

At least 37.5 per cent alcohol in the bottle, distilled to below 96 per cent, not flavoured, at most 20 grams of sweetening per litre and only caramel for colour.

Regulation (EU) 2019/787 lists 44 categories of spirit drinks, and rum is the first of them. Anyone who puts the name rum on the label abides by that list. Adding alcohol is not allowed, nor is flavouring. Sweetening is permitted to round off the taste, with a hard upper limit of 20 grams per litre, expressed as invert sugar. Within those limits there is still plenty of room, and you can taste that room in the bottle.