@toolman1990 Thank you for suggesting that I could have been more clear in my question and comments about network timing behaviors. I'll try to clear up some misunderstandings about the source of cable time information signals.
The Spectrum network master clocks do not change their time signals forward or back one hour in the spring and fall. Instead devices with a time display (normally only a DVR or set-top tuner) are programmed by Charter Comm and other system operators to offset their time displays forward or back from the cable network clock time on the appropriate dates. The eMTA modems used for Spectrum VoIP telephone service do not send any date and time signals to telephone instruments connected to the in-home wiring that plugs into the Phone1 or Phone2 jacks.
This customer @Downeast has two (presumably customer-provided) AC outlet powered telephone instruments which display date and time. The customer programs those details into the phone unit, and his stated problem is that those units do not keep time reliably. His goal is to stabilize the displayed time so it matches his watch, wall clock, or cellphone throughout the day.
Feel free to contribute.
The information you posted is incorrect since they do update for daylights savings time for years. Spectrum Digital Phone sends the time and date via the caller id information which is what the phone uses to automatically update the time and date. I have had their phone service for years and the date and time have always updated during the time change. So if Spectrum is sending out the incorrect time and date on their caller id information then that is a Spectrum issue they will need to correct and the OP will have to wait for the escalation ticket to work its way up the chain until they fixed the issue.
The issue has been nicely summarized. Spectrum pushes a time hack to connected devices. My phones, which I have had since my days on UVerse, accept that time code but do not have any setting available to establish the time zone desired. The phones sets thus display UTC not Local time.
Ultimately, nothing Spectrum can do to resolve the problem, and short of buying a new set of phones (not gonna waste my money) the time will always remain incorrect on the display. I guess I have to live with it!