What does the Spanish New Year's Eve tradition of eating 12 grapes symbolize?

In the Spanish New Year's Eve tradition, eating 12 grapes symbolizes the 12 months of the year.

The custom is known as las doce uvas de la suerte, or “the twelve grapes of luck.” Participants try to eat one grape with each stroke of midnight, traditionally linking each grape with a month in the coming year. Finishing the sequence is popularly associated with good fortune.

The practice became especially prominent in Spain in the early twentieth century. A widely repeated origin story connects its spread to a surplus grape harvest in 1909, when growers promoted grapes as a New Year's product. The exact development of the custom is more complex, because earlier elite celebrations had already used grapes.

The tradition has also spread to parts of Latin America. The grapes are not meant to represent the zodiac, apostles, or Christmas days; the standard symbolism is the calendar's twelve months.