According to researchers from Uppsala University in Sweden one can somehow mtickle electrons into higher energy state atoms.

By nudging electrons into a higher energy state (the Rydberg state) you can amass significant information about time without ever having to start the clock.

“You just look at the interference structure and say ‘okay, it’s been 4 nanoseconds”, says physicist Marta Berholts from the University of Uppsala in Sweden, who led the team, explained to New Scientist.

Electrons, “being quantum animals” , though, their movements are less like beads sliding about on a tiny abacus, and more like an evening at the roulette table, where every roll and jump of the ball is squeezed into a single game of chance.”

“By looking for the signature of interfering Rydberg states amid a sample of pump-probe atoms, technicians could observe a timestamp for events as fleeting as just 1.7 trillionths of a second.”

More here.