If you’ve had the same clock plugged in next to your bed forever you may want to check that it has the right time. Researchers from the National Institute of Standards and Technology and the U.S. Naval Observatory have found that because of a change in federal energy regulations, your clock might be gaining or losing a few seconds over time. This is because electric clocks keep time based on the usually stable and precise pulses of electic current that powers them; exactly 60 hertz (cycles per second) in the U.S. In the past, regulators required power companies to immediately correct the rate if it deviated from 60 hertz, but that precision is expensive to maintain. So last year the Federal Energy Regulatory Commission quietly eliminated the requirement. Energy officials say other standards will keep clocks in check, and so far the problem has not amounted to more than a few seconds here and there. However, scientists investigated and found without the time correction rule clocks could gradually lose track of the correct time if the grid’s power was delivered at consistently higher or lower rates. Study co-author Demetrio Matsakis says between time changes in March and November (when clocks are reset), the time on clocks plugged into the walls could drift by as much as seven and a half minutes.