at an even or an odd nanosecond?

Failed to get "at an even or an odd nanosecond."
It seems easy to understand "at a nanosecond." At an even nanosecond? Does it mean "at an only nanosecond"? And "at an odd nanosecond" refers to "at more than a nanosecond"?

Context:

Cosmic light
To minimize the risk of a conspiracy, both Zeilinger’s and Friedman’s teams are looking to the skies — in particular at light coming from energetic cosmic objects known as quasars. The plan is to set up a standard entanglement test in the laboratory. While it is running, the researchers will also measure light coming from two quasars on opposite sides of the sky. On the basis of, for instance, whether the light from the first quasar hits their telescope at an even or an odd nanosecond, they would then make a decision about which two properties of their first entangled particle to observe. They would similarly decide what measurements to make on the second entangled particle, on the basis of the arrival time of the light from the second quasar.

More:
http://www.nature.com/news/cosmic-light-could-close-quantum-weirdness-loophole-1.14771