Universal Time (UT) is based on Earth's rotation, with Universal Time 1 (UT1) incorporating corrections for Earth's axial wobble. The current global standard, Coordinated Universal Time (UTC), is derived from International Atomic Time (TAI) and maintained by the International Bureau of Weights and Measures (BIPM). Due to atomic time's greater stability, UTC and UT diverge over time.

Since 1972, UTC has been adjusted with leap seconds to keep its difference from UT1 under 0.9 seconds. These adjustments are made by the International Earth Rotation Service (IERS) either on June 30 or December 31 when necessary. To date, 27 positive leap seconds have been added, resulting in UTC being 37 seconds behind TAI.

Given the challenges leap seconds pose to precision systems, the 2022 General Conference on Weights and Measures (CGPM) proposed relaxing the 0.9-second limit between UT1 and UTC. The final decision on the leap second system is expected at the 2023 World Radiocommunication Conference