KRISS Introduces UTCk 4 to Provide Public Access to Korea Standard Time

- Free software synchronizes PCs and servers with Korea's most precise official time -

The Korea Research Institute of Standards and Science (KRISS, President Lee Ho Seong) has developed and released UTCk 4, a standard time synchronization program that allows users to precisely align the time on their personal computers and servers with Korea Standard Time (KST).

TCk 4 is a Network Time Protocol (NTP)–based program that uses Korea Standard Time generated by KRISS. It enables internet-connected devices to compare their system time with KST and synchronize it with an accuracy of within 0.1 seconds. The program is available for free download via the UTCk 4 webpage (www.kriss.re.kr/time).

▲ (Left) UTCk 4 webpage; (Right) UTCk 4 in operation

Personal computers generate their own time using a device called a quartz oscillator. When this device is affected by external factors such as temperature and humidity, fluctuations occur in the frequency it generates, leading to discrepancies between a computer's system time and the standard time. Such time errors can cause everyday inconveniences—such as failed concert ticket reservations or university course registrations—as well as more serious societal disruptions, including errors in securities trading and failures in national communication networks.

One of the most widely used technologies to address this issue is the Network Time Protocol (NTP). NTP synchronizes a computer's system time by receiving accurate time information from a reference time server. However, if the time provided through NTP is inaccurate, all devices synchronized to that source will also reflect incorrect time, potentially leading to widespread problems. For this reason, NTP must be linked to the most accurate time source available in order to provide reliable services.

As Korea's National Metrology Institute, KRISS generates and maintains UTC(KRIS), Korea's real-time realization of Coordinated Universal Time (UTC), which serves as the basis for Korea Standard Time. Korea Standard Time is generated using one cesium atomic clock, five hydrogen masers, and an in-house developed frequency standard, and its accuracy is maintained through regular comparisons with UTC. As a result, Korea Standard Time is kept accurate to within a few nanoseconds (billionths of a second) of UTC.

▲ KRISS development team for UTCk 4

To enable the convenient use of Korea Standard Time in daily life and industrial settings, KRISS has developed and operated the UTCk standard time synchronization program since 2002. However, the previous version, UTCk 3.1, faced limitations in handling large-scale traffic due to restricted internal server capacity. With the newly developed UTCk 4, the server infrastructure has been migrated to a cloud-based environment, eliminating access bottlenecks and enabling the system to handle up to approximately 45 million requests per hour.

The pilot operation of UTCk 4 is currently underway, with official service scheduled to begin on February 1, 2026. The previous version, UTCk 3.1, will be fully discontinued at midnight on January 31. To avoid service interruptions, existing users are advised to install the latest version before February 1, when official operation begins.

Jeon Myoung Hun, Head of the Office of IT Management at KRISS, stated, "UTCk 4 was designed to significantly enhance system scalability in response to growing user demand, while also strengthening security measures to provide safer and more stable time synchronization."

Dr. Heo Myoung Sun, Head of the Time & Frequency Group at KRISS, stated, "KRISS will continue its efforts to ensure that Korea Standard Time contributes to the public's daily convenience and the reliable operation of national systems."