# Binary clock

A binary clock is a clock which displays traditional sexagesimal time in a binary format. Originally, it showed each decimal digit of sexagesimal time as a binary value, but presently true binary clocks also exist. Most binary clocks are digital, although analog varieties exist.

## Binary-coded decimal clocks

Reading a BCD clock: Add the values of each column of LEDs to get six decimal digits. There are two columns each for hours, minutes and seconds.

As of 2008, the most common binary clocks sold are designed by Anelace Inc., and uses six columns of LEDs to represent zeros and ones. Each column represents a single decimal digit, a format known as binary-coded decimal (BCD). The bottom row in each column represents 1 (or 20), with each row above representing higher powers of two, up to 23 (or 8). To read each individual digit in the time, the user adds the values that each illuminated LED represents, then reads these from left to right. The first two columns represent the hour, the next two represent the minute and the last two represent the second. Since zero digits are not illuminated, this clock is not usable in the dark.

To read a BCD clock add the values of each column of LEDs to get six decimal digits. This gives two decimal digits each for hours, minutes, and seconds.

In binary:
0 -> 0
1 -> 1
2 -> 10
3 -> 11
4 -> 100
5 -> 101
6 -> 110
7 -> 111
8 -> 1000
9 -> 1001

Since if numbers were displayed this way you could not tell the difference between 1, 2, 4, and 8. All numbers are padded with leading zeros, so as to be four digits.
Thus:
0 -> 0000
1 -> 0001
2 -> 0010
3 -> 0011
4 -> 0100
5 -> 0101
6 -> 0110
7 -> 0111
8 -> 1000
9 -> 1001
(light = 1, dark = 0)

## True binary

The latest version of the Anelace Inc. binary clock can also use just true binary to give the time (one number each for hours, minutes, and seconds) rather than six numbers for the decimal digits of the time units. Numbers are then displayed horizontally:

Time Technology's Samui Moon true binary wristwatch.

Hours Minutes Seconds 1 1 0 1 1 0 0 0 1 0 1 0 0 0 1 1
A binary clock circuit displaying 00:08:04.

The above display uses three binary number columns, one for each of the units (hours, minutes and seconds) of the conventional time system.