You actually can still call NIST and hear the signal broadcast from WWV[0], though that's probably different from the telephone time of day you're thinking of, which might have come from one of these machines [1] in a local telephone exchange.

[0] https://www.nist.gov/pml/time-and-frequency-division/time-di...

[1] https://en.wikipedia.org/wiki/Audichron