Ha, I built something like that 25 years ago and it is still going.
I used only two concentric LED rings, the outer, 12 led, ring indicated the hours, the inner, 60 led, ring the minutes and seconds. The minute is illuminated by a single led and the second has a 'comet tail' that overtakes the minute - neat to watch.
I never bothered with the pendulum display.
My first clock used TTL chips and was a bit power hungry (for the standby battery), the second version used C-mos chips and the larger, 5mm LED's and used only 1/10th of the power.
I built these for the challenge in doing the artwork of the circular PC boards for them, the TTL version uses 6 stacked boards,of about 100 mm diameter. The C-mos version uses two boards of about 150 mm diameter.
Have fun, the circuit is easy, the boards are the hard part :wink:
Klaus