In article 3bb8952f-1316-4b1a-aaee-a773ee2fe244
@v31g2000vbs.googlegroups.com, says...
but did the frequency go down with the volts? I have a far eastern
LED Lloytron clock that seems to sync to the mains. If the frequency
goes down the clock runs slow.

Almost all LED clocks are mains synched. Since they have to be mains
powered anyway (yeah, mostly) then they're already connected to a well
regulated (by statute) frequency source.

As it happens, I have an exception, an LED clock that uses the RDS data
to set the time, though in the absence of decent reception it seems to
cope tolerably - presumably off the mains frequency or a crystal.

--
Skipweasel - never knowingly understood.