In high school I had one of the mechanical "flip" clocks. Then later an LED clock which almost certainly used the LM8560 (a Sony, which lasted far longer than I expected. Back when products were built with quality in mind). And as the article says, the chip depends on the AC frequency (50/60 Hz) to keep accurate time. For the US market, that input was likely hardwired to 60 Hz via a jumper. Japan must have used a switch, given it's mixed 50/60 Hz national power standard.

These days I have an LCD clock that does not use the LM8560 but instead gets it's time from the Radio Data System values embedded in the FM broadcast. Possibly using the Sanyo LC72723 to decode them. The CT (clock Time & Date) data field is accurate to within 100ms according to wikipedia:

https://en.wikipedia.org/wiki/Radio_Data_System