This project is a second entry to the One Hertz Challenge. The quote to Jim Valvano on the description came by chance when I was doing an image search for the project banner, and it ended naming the clock. 

The purpose of this clock is to count the day time in seconds, either up or down. Nothing fancy.

The circuit is built upon an Arduino Nano, a DS3231 RTC module, a SSD1306 128x64 OLED module and one button to select up/down counting an to show and set the time in HH:MM:SS format.

The software uses the DS3231 and u8g2 libraries to interface the RTC and the OLED display, respectively. A custom function debounces the button and return two kind of events: Pulses and Long presses. The user interface is a state machine that ticks every 10ms (roughly) and the states changed depending upon the button events. 

Here's a short video of the clock working.