It would be silly for companies to miss this. But history isn't on the optimists' side. Lab equipment software used by heart surgeons at Papwoth Hospital in the U.K. couldn't function Feb. 29, so the lab analysis had to be done by other labs using a different vendor's equipment. A higher taxicab fare in New York went into effect March 1. But meters programmed by one company in Queens forgot about the leap day and charged the higher rate on Feb. 29.
Vigilance is the key.
But it proves that there's never complete assurance in third-party software.