Clock is controlled by the 6502 Retro Controller Board - described in one of my earlier projects. This original boards hes been supplemented with two additional PCBs.

First one holds set of four seven segment displays with their drivers and some glue logic. There is also M6242B RTC chip and set of four buttons.

Second board is a little bit more complicated with power circuit, UART chip, timer/counter chip nd famous SP0256-AL2 speech synthesis chip. Timer chip (MC6840) is used not only to generate system "ticks" but also tu measure length of pulses coming from DCF77 module. However function of automatic time synchronization is still in development and requires some fixes.