New York’s stores and restaurants struggling after the pandemic have a new headache, besides inflation and crime. A state court’s aggressive reinterpretation of a more-than-century-old law puts businesses on the hook for, potentially, billions of dollars in unexpected costs. If you have a job, you probably get paid every two weeks — the most common schedule by which employers pay workers. The federal government pays workers every two weeks, as does the city. New York law has long carved out an exception: “A manual worker shall be paid weekly.” The weekly pay provision goes back to 1890, when the Legislature held that “every manufacturing, mining or quarrying, lumbering, mercantile . . . corporation . . . shall pay weekly.” The purpose, as discussion around a 1935 amendment made clear, was to “protect the employees of” firms and individuals “who would set up business . . . , defer the payments of wages” and then “disappear.”