In article ,
"Howard Kowall" wrote:

I wanted both clocks in 24hr mode,so I goggled the clock IC used in the
digital clock,and found most of the using a very general purpose clock IC
and all capable of doing 24hrs format buy a small modification,usually this
mod is just a matter of shorting a couple of pins on the IC

Howard-

I built a clock from Radio Shack plans and parts back in the 1970s.
That chip had the 24 hour option, but used the same pin to change from
60 Hz to 50 Hz! I got around that by using an SN7410 to convert 60 Hz
to 50 Hz.

Fred