To ensure that 20 cameras show the same synchronized date and time in Live View, the best method is to synchronize the date and time with a remote NTP (Network Time Protocol) server. NTP servers are designed to synchronize clocks of network devices, ensuring accurate and consistent timekeeping across all connected devices. This method is reliable and commonly used in networked environments to maintain time synchronization across multiple devices.
References: Axis Communications Network Video Product Manual - Time and Date Settings.