Automachron

Easy to use Win-32 freeware keeps your PC in sync

NIST Time Service

National Institute of Standards and Technology time synchronization resources

NTP.org

Network Time Protocol project home page and software distribution

Pool.ntp.org

Worldwide cluster of NTP servers providing reliable time sync

PTB Time Server

Physikalisch-Technische Bundesanstalt official time and frequency services

Time Synchronization Server

provides the latest information on Network Time Protocol (NTP) and other related clock synchronization products

USNO Time Service

USNO monitors the Global Positioning System (GPS) constellation and provides system timing offsets to the U.S. Space Force 2nd Space Operations Squadron (2SOPS).