What does NTP stand for?

NTP stands for Network Time Protocol, the networking standard that synchronizes computer clocks across packet-switched networks.

Designed by David L. Mills at the University of Delaware, NTP grew out of experimental Internet time-synchronization work in the late 1970s and early 1980s. It was introduced in 1985 and remains one of the oldest Internet protocols still widely used. NTP clients compare timestamps with one or more time servers and estimate both clock offset and network delay.

NTP normally aims to keep systems within a few milliseconds of Coordinated Universal Time. It commonly uses UDP port 123 and organizes time sources into strata: highly accurate reference clocks are at stratum 0, while networked servers occupy higher-numbered levels. A higher stratum number indicates distance from the reference source, not necessarily worse real-world quality.

A common mix-up is confusing NTP with SNTP, or Simple Network Time Protocol. SNTP uses the same on-wire format but omits much of NTP's filtering, redundancy, and clock-discipline logic. NTP also supplies UTC synchronization, not time-zone or daylight-saving information.