It is very rare for honey to go bad. Honey will ferment if it's moisture content gets too high (harvested before it is capped by the bees or you add water to it). Provided the honey hasn't been contaminated in some way, it will keep for many, many years.
Honey will crystalize, and separate. Honey is made up to two types of sugar - glucose and fructose, with varying percentages . The glucose will crystalize before fructose, which forms large crystals, often leaving behind the liquid fructose. The higher the glucose, the faster it till crystalize. Glucose is good for you, fructose not so much (even though they use fructose to sweeten food in the form of corn syrup, and is actually major contributor to obesity). Therefore, the faster the honey crystalizes, the higher the glucose, the better it is for you.
The crystallization will dissolve again if you can keep your honey at 37-38 deg C for a few days, or, just stir it up and get used to eating crunchy honey. Don't be tempted to over heat it or heat it in the microwave. This will destroy all the natural goodness of the honey.
Another option is to add more water and make honey mead.
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