A binary clock is usually a clock

Clock

A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece...

 which displays traditional sexagesimal time

Time

Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

 in a binary

Binary numeral system

The binary numeral system, or base-2 number system, represents numeric values using two symbols, 0 and 1. More specifically, the usual base-2 system is a positional notation with a radix of 2...

 format. Originally, it showed each decimal digit of sexagesimal time as a binary value, but presently binary clocks also exist which display hours, minutes, and seconds as binary numbers. Most binary clocks are digital

Digital

A digital system is a data technology that uses discrete values. By contrast, non-digital systems use a continuous range of values to represent information...

, although analog

Analog signal

An analog or analogue signal is any continuous signal for which the time varying feature of the signal is a representation of some other time varying quantity, i.e., analogous to another time varying signal. It differs from a digital signal in terms of small fluctuations in the signal which are...

 varieties exist. True binary clocks also exist, which indicate the time by successively halving the day. Thus these clocks do not use hours, minutes, or seconds. Similar clocks, based on Gray code

Gray code

The reflected binary code, also known as Gray code after Frank Gray, is a binary numeral system where two successive values differ in only one bit. It is a non-weighted code....

d binary, also exist.

Binary-coded decimal clocks

As of 2008, the most common binary clocks sold are designed by Anelace Inc., and use six columns of LED

LEd

LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

s to represent zeros

0 (number)

0 is both a numberand the numerical digit used to represent that number in numerals.It fulfills a central role in mathematics as the additive identity of the integers, real numbers, and many other algebraic structures. As a digit, 0 is used as a placeholder in place value systems...

 and ones. Each column represents a single decimal digit, a format known as binary-coded decimal

Binary-coded decimal

In computing and electronic systems, binary-coded decimal is a digital encoding method for numbers using decimal notation, with each decimal digit represented by its own binary sequence. In BCD, a numeral is usually represented by four bits which, in general, represent the decimal range 0 through 9...

 (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

Light-emitting diode

A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...

 represents, then reads these from left to right. The first two columns represent the hour

Hour

The hour is a unit of measurement of time. In modern usage, an hour comprises 60 minutes, or 3,600 seconds...

, the next two represent the minute

Minute

A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units...

 and the last two represent the second

Second

The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....

. Since zero digits are not illuminated, the positions of each digit must be memorized if the clock is to be usable in the dark.

How to read binary

In binary:

0 -> 0

1 -> 1

2 -> 10

3 -> 11

4 -> 100

5 -> 101

6 -> 110

7 -> 111

8 -> 1000

9 -> 1001

10-> 1010

11-> 1011

12-> 1100

If numbers were displayed this way you could not tell the difference between 1, 2, 4, and 8, therefore 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)

Binary Coded Sexagesimal

The latest version of the binary clock can also use binary coded sexagesimal (base 60) 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:

	Hours	Minutes	Seconds
32		1	1
16		0	1
8	1	0	0
4	0	1	0
2	1	0	0
1	0	1	1
	10	37	49

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

External links

• Binary clock made in Flash
• Binary clocks as applications (for Windows)