rest evenly dividing every gēng into 6 equal parts. Describing the time during the night Gēng and diǎn were used together to precisely describe the time at night. Counting from the first gēng to the next would look like this: yìgēng (), yìgēng 1 diǎn (), yìgēng 2 diǎn (), yìgēng 3 diǎn (), yìgēng 4 diǎn (), yìgēng 5 diǎn (), èrgēng (). Given the time sāngēng 2 diǎn (), you would read it as "two diǎn after sāngēng", and find the time to be 00:48. The night length is inconsistent during a year. The nineteenth volume of the Book of Sui says that at the winter solstice, a day was measured to be 60% night, and at the summer solstice, only 40% night. The official start of night thus had a variation from 0 to 1 gēng. This variation was handled in different ways. From the start of the Western Han dynasty in 206 BC until 102 AD, yìgēng was moved back one kè every 9th day from the winter solstice to the summer solstice, and moved forward one kè every 9th day from summer solstice to the winter solstice. The Xia Calendar (), introduced in 102 AD, added or subtracted a kè to the start of night whenever the sun moved 2.5° north or south from its previous position. Traditional units in context Modern applications Chinese still uses characters from these systems to describe time, even though China has changed to the UTC standards of hours, minutes, and seconds. Shí is still used to describe the hour. Because of the potential for confusion, xiǎoshí (, literally "small hour") is sometimes used for the hour as part of a 24-hour cycle, and shíchen () is used for the hour as part of the old 12-hour cycle. Diǎn is also used interchangeably with shí for the hour. It can also be used to talk about the time on the hour—for example, 8 o' clock is written as 8 diǎn (). Fēn is also used for minutes. To avoid confusion, sometimes the word fēnzhōng (, literally "clock minute") is used to clarify that one is talking about modern minutes. The time 09:45 can thus be written as "9 shí, 45 fēn" () or "9 diǎn, 45 fēn" (). Kè has been defined as of a day since 1628, so the modern kè equals 15 minutes and each double hour contains