Nystrom's "Tonal Watch, or Clock-dial". Note the use of his invented digits for hex values 9-F. Also note that midnight (hour 0) is at the bottom, rather than the top of the clockface.

Hexadecimal time is the representation of the time of day as a hexadecimal number in the interval [0,1).

The day is divided in 1016 (sixteen) hexadecimal hours, each hour in 10016 (two hundred and fifty-six) hexadecimal minutes and each minute in 1016 (sixteen) hexadecimal seconds.

## History

The time may have been used during the Tang Dynasty (7th-10th centuries) in China. [1]

This time format was proposed by the Swedish-American engineer John W. Nystrom in 1863 as part of his tonal system.

In 1997, the American Mark Vincent Rogers of Intuitor proposed a similar system of hexadecimal time and implemented it in JavaScript as the Hexclock.

## The system of Rogers

A day is unity, or 1, and any fraction thereof can be shown with digits to the right of the hexadecimal separator.
So the day begins at midnight with .0000 and one hexadecimal second after midnight is .0001.
Noon is .8000 (one half), one hexadecimal second before was .7FFF and one hexadecimal second before next midnight will be .FFFF.

Intuitor-hextime may also be formatted with an underscore separating hexadecimal hours, minutes and seconds. For example:

### Clock

HexHex (Boardman)ISO 8601Comment
.01000_10_000:05:37.5
.02000_20_000:11:15
.04000_40_000:22:30
.08000_80_000:45:00
.10001_00_001:30:001.5÷24 = 1÷16 = 0.1
.80008_00_012:00:0012÷24 = 8÷16 = 0.8
.F000F_00_022:30:0022.5÷24 = 15÷16 = 0.F
.F800F_80_023:15:00

Hex=/≈hexsec
base 16
=/≈hexsec
base 10