Network Time Server

Synchronization with a Network Time Server is a feature of the Date & Time control panel that was introduced in Mac OS 8.5 and continued through Mac OS 9.2.2.

Usage
The option to Use a Network Time Server enables a Mac to synchronize its date and time information via the Network Time Protocol (NTP) with supported atomic clocks on the Internet. An active Internet connection is required for automatic synchronization.

Replacement
Mac OS X replaced the classic control panel with System Preferences. The time synchronization features were carried over into the Date & Time pane. Due to security concerns, Apple no longer relies on NTP to connect to its own time servers as of macOS Mojave (10.14) in 2018 and instead implemented its own timed function.