Telephone Time

Back in the day if you needed to know the time to set your clocks you called the telephone operator and asked her for the time. Over time this became a dedicated service where an operator would site in front of a microphone reading out the time, and anyone could call in and listen to her reading the time. In time it became an automated service, with a computer reading off the time.

Now in 2021, with mobile phone with network set time everywhere, this service still exists and continues to be free.
In the United States it is a service provided by the U.S Naval Observatory. USNO provides both voice announcements of the time, and services to synchronize systems over telephone modems.

Voice Announcers
The voice announcements have the same pattern at both sites, and always begin with the local time (daylight or standard). The local time announcements are made on the minute, and 15, 30, and 45 seconds after the minute. Coordinated Universal Time (UTC) is announced five seconds after the local time.
Time Voice Announcer, Washington, DC:
202-762-1401
202-762-1069

Time Voice Announcer, Colorado Springs, CO:
719-567-6742