A binary clock is usually 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 binary clocks also exist which display hours, minutes, and seconds as binary numbers. Most binary clocks are digital, although analog varieties exist. True binary clocks also exist, which indicate the time by successively halving the day, instead of using hours, minutes, or seconds. Similar clocks, based on Gray coded binary, also exist.