Binary clock

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A binary clock shows the time of day using binary numbers (0s and 1s). There are digital and analog versions, and some clocks tell time by splitting the day into binary fractions.

Common designs
- Six LED columns (BCD): Each column holds one decimal digit. The bottom LED is 1, with each higher LED representing higher powers of two up to 8. The first two columns are hours, the next two are minutes, and the last two are seconds. To read, add the values of the lit LEDs in each column. Zero digits stay dark, so you may need to remember which positions correspond to which digits in the dark.
- Binary-coded sexagesimal: Each time component (hours, minutes, seconds) is shown as its own binary number. This uses up to 6 bits per component. For 24-hour clocks, there are 11 or 17 LEDs: 5 for hours, 6 for minutes, and 6 for seconds (seconds are not used in the 11-LED version).
- Three-line format: Hours, minutes, and seconds can be shown on three separate lines instead of in columns.
- True binary clocks: Some clocks divide the day itself into halves, quarters, etc., using a binary representation of the day rather than separate hours, minutes, and seconds.

Other variations
- Day fractions: A clock can represent time as binary fractions of a day (for example, ½ day, ¼ day), using 16 bits. The smallest unit would be about 1.3 seconds. An analog version of this idea also exists.
- Hexadecimal time: Because binary fractions describe time well, some people describe these clocks in hexadecimal time for easier writing.