If 180 LEDs are too many to consider, how about 132? I think a reasonable compromise would be 48 LEDs for the hours, 60 for the minutes, and 24 for the seconds. It would require 12 pins for charlieplexing instead of 14 pins for 180 LEDs. The hours would advance every 15 minutes, the minutes every minute, and the seconds every 2.5 seconds.
