A yearlong experiment with America's electric grid starting this summer could mess up traffic lights, security and home automation systems and some computers, as first reported by the Associated Press. "A lot of people are going to have things break and they're not going to know why," says Demetrios Matsakis, head of the time service department at the U.S. Naval Observatory, one of the official timekeeping agencies in the federal government.

Since 1930, electric clocks have kept time based on the rate of the electrical current that powers them. If the current slips off its usual rate, clocks run a little fast or slow. Power companies now take steps to correct it and keep the frequency of the current — and the time — as precise as possible. The group that oversees the U.S. power grid is proposing an experiment that would allow more frequency variation than it does now without corrections, according to a company presentation obtained by the Associated Press.

Officials say they want to try this to make the power supply more reliable, save money and reduce what may be needless efforts. The test is tentatively set to start in mid-July, but that could change.