Humble Pi: When Math Goes Wrong in the Real World

by Matt Parker

The problem continues to inconvenience people. At five p.m. on September 6, 2017, mathematician James Propp was in a Verizon Wireless phone store in the US, buying a new phone. It was for his son, and thankfully, it came with a no-questions-asked refund policy if returned within fourteen days. As it turns out, the phone was not what his son was after, so two weeks later, on September 20, Propp senior went back to return it. But despite it being less than fourteen days since he had bought the phone, the store could not complete the return, as it was now technically day fifteen of the contract. It seems that Verizon started counting at day one and not at day zero and they used the day number as a way to measure the passing of time. So as soon as James received the phone, Verizon already figured he’d owned it for a whole day. By the start of day two, in Verizon’s system he’d had the phone for two days, even though he’d only received it about seven hours before, and so on and so on, eventually leading to James holding a phone he’d had for less than fourteen days and Verizon claiming he’d owned it for fifteen.