So how long is a nanosecond, or a billionth of a second? By comparison, a typical lightning flash lasts about 10 milliseconds, or 10,000,000 nanoseconds. So when we say "time flies", the nanoseconds are, indeed, flying by quickly! But highly precise time is critical to accurate GNSS position calculations. This GPS World article reports how Galileo System Time (GST) is being synchronized with UTC time, although it does not need to be in order for the Galileo satellites to function correctly. The article also provides a good refresher on the basic functionality of GNSS navigation, with a cursory explanation of how a satellite's location is calculated.