IMHO: Telephone time services have never been exact to NIST. I have no idea
if any of them had ever tried to be.

Many years ago, (the mid 70's), during "nothing to do" time at work I would
dial the time services in NY, Boston, Philadelphia and a few other places.
There was usually a difference of 4-10 seconds between them. Using NYC as
the standard, Philly would be 7 seconds behind and Boston 4 seconds early.
From week to week the difference between them might also change. NY was
about 2 seconds off the top of hour chime on CBS radio, but once it went 15
seconds slow to the radio.

FWIW; I also learned that you couldn't dial the time service in another time
zone.

"qquito" wrote in message
ups.com...
Hello, All:

I bought a so-called "atomic clock" two days ago, and it receives the
radio signals from NIST (National Institute of Standards and
Technology) to automatically adjust its time. And it works fine.

Meanwhile, I called the Verion telephone number [(757)622-9311 in
southern Virginia] which gives current time. To my surprise, I found
that the Verizon time is about four (4) seconds faster than the NIST
time.

What is the cause of this difference? Is it due to telephone
transmission delay? Or does Verizon use an independent clock that is
not synchronized with NIST?

Thanks for reading the replying.

Roland