when one is up to 100 ms faster than the other. Note that neither frequency synchronization nor phase synchronization deals with the actual time of the day. The final term, time synchronization, is about providing a date and time that people can agree on. More correctly, it is phase synchronization combined with a count of the passage of time since a defined starting point (called an epoch). If everyone agrees with the starting point of time (epoch) and the rate at which time passes (frequency), then everybody is synchronized in date and time. Here our music analogy breaks down somewhat. Let's assume that a concert is scheduled to start at 7 p.m. (19:00) on July 15, and SO anybody who wants to be in the audience to hear the event should be present by that time. But this requires that the current date and time are agreed upon SO that everybody understands when that concert will begin. Therefore, time synchronization is useful for communicating an absolute point in time by giving it a value; or by recording an event and being able to place it in sequence with other events (building a timeline). So, the evening news starts daily at 10 p.m. (22:00:00) local time and Brexit occurred at 31-Jan- 2020 23:00:00 GMT. Of course, for this scheme to work, all our clocks must be time synchronized to an agreed time reference. You are probably very familiar with time synchronization from experi- ence with everyday mobile phones, computers, and smart watches, as they are automatically time synchronized from the network, unlike the older wristwatch. Frequency Synchronization As previously stated, frequency synchronization is simply the capability to make two things vibrate or oscillate at the same frequency or rate. This is what the piano tuner does, and why all the players in the orchestra adjust their instruments before a concert-they are "frequency synchronizing" their instruments. Those instruments that are correctly frequency synchronized are said to be "in tune," while a timing expert would say they are "frequency synchroniz