Your smartphone is probably losing track of time. Most electronics with internal clocks keep them regulated via vibrating crystals (much like a quartz clock) that keep their timekeeping precise. But while far better timekeepers than mechanical clocks, even these crystals can be thrown off their regular frequencies by external factors like humidity or temperature. Which is why scientists at Hong Kong University of Science and Technology think you’re better off syncing your clock to your overhead lights.

Smartphone clocks can drift by up to 10 seconds a day, and if you’re one of the many people who rarely syncs up your handheld with your computer or otherwise docks with some mothership computer online, that means you could pretty quickly start drifting by whole minutes.

But artificial lighting is all around us, and it to is a fantastic keeper or time. Alternating current provided by power mains runs at a frequency of 50 or 60 cycles per second, with the power delivered dropping to zero twice per cycle. The fluorescent lights in your home or office are actually flickering at very regular intervals, though its too rapid a flicker for your eyes to notice it. The Hong Kong UST team has demonstrated that any device with a camera or light sensor--so pretty much any smartphone currently marketed--can tap this flicker to keep accurate time, just like the oscillations of its internal crystals.