Precise is not a term that's often used when considering clocks in the unqualified sense. The two usual dimensions you consider are accuracy and stability. Ac

Precise is not a term that's often used when considering clocks in the unqualified sense. The two usual dimensions you consider are accuracy and stability. Accuracy is about how well your clock tracks the target timebase over a long period, like a month. If your clock is free-running then this is important to you. Many kinds of clocks have aging effects, meaning that they become less accurate over time. Stability is about whether the individual "ticks" of the clocks have the same duration. Phase noise and clock stability are the same thing, so if you're using your clock to generate radio frequencies, this might actually be more important to you than accuracy. A clock can be accurate but unstable, or stable but inaccurate and so on. The most accurate clock technology is the atomic clock. The high-end of that market is represented by cesium standards, with rubidium standards at the lower-end. The most stable clocks outside the laboratory setting are ovenized crystal oscillators (OCXO). This is fundamentally a quartz crystal inside a metal box with a heater to keep a constant temperature. The next aspect is clock disciplining. Unless you intend to run your clock free and rely on its fundamental accuracy, you're probably going to synchronize it vs a superior standard. A common option for clock discipline is GPS, i.e. you're synchronizing your clock to the atomic clocks of the GPS satellites. NTP is simply a network-based mechanism for disciplining a clock. If you want "better NTP", that's called "PTP" but it's really only a local-area network thing.