There is only one store on the island of Tristan de Cunha. Being a six-day journey from Cape Town means that the islanders can't rely on standard grocery store fare, so though the shop provides some basics, everyone on Tristan also helps out raising livestock and farming potatoes. It's this kind of subsistence farming that keeps the islanders fed. And because everyone works a variety of jobs and pools resources, they can afford to declare that everyone gets three weeks of vacation around Christmas (everyone on the island is, reportedly, a practicing Christian—there are two churches for 293 residents). That means that the store closes. And that means that if you think you might need anything from the store in that three week gap, you will need to stock up in advance.