A binary clock is a different kind of clock, that displays the time in a binary format...
A binary clock, also known as the powers of 2 clock, displays the time in binary format. It has columns of LED lights that can be interpreted as binary numbers. The first two columns show hours, the middle two columns show minutes, and the last two columns show seconds. Decoding the reading takes a bit of practice but is quite simple. There are two ways to decode clock reading. We can read it in binary-coded decimal (BCD) mode or in direct binary mode. In the BCD mode, each row represents a power of 2. From the bottom row upwards, powers of 2 increase (0...8). In direct binary mode, each column represents some power of 2. From right to left, powers of 2 increase (0...32). Depending on where the LED light is lit, the numbers are added together and the clock reading is obtained in a more familiar format.
More information on decoding a binary clock reading can be found in the article "How to decode a binary clock".