Reference and tracker for the lunar time standard.https://lunartime.org/enhttps://lunartime.org/learn/china-and-lunar-time/https://lunartime.org/learn/china-and-lunar-time/A group at the Purple Mountain Observatory published LTE440, software that computes Lunar Coordinate Time. What its papers state, and what they do not.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/how-lunar-time-will-be-realized/https://lunartime.org/learn/how-lunar-time-will-be-realized/A definition is not a time scale. Somebody has to run clocks on the surface, clocks in orbit and a weighted average. Here is what has been proposed.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/how-utc-works-and-how-ltc-will-mirror-it/https://lunartime.org/learn/how-utc-works-and-how-ltc-will-mirror-it/UTC is TAI minus whole leap seconds, and TAI is a weighted average of hundreds of atomic clocks. A lunar scale would repeat four of those five steps.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/lunar-time-for-developers/https://lunartime.org/learn/lunar-time-for-developers/How to timestamp lunar data today: record UTC, keep the model offset separate, name both scales. What the JSON API and the lunar-time package actually do.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/lunar-time-vs-lunar-calendar/https://lunartime.org/learn/lunar-time-vs-lunar-calendar/Lunar time is a question about the rate of a clock. A lunar calendar is a question about dates and sunlight. This site covers the first and not the second.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/time-scales-family-tree/https://lunartime.org/learn/time-scales-family-tree/TCB, TCG, TT, TAI and UTC form one chain. TCL branches off at the top for the Moon. What each scale is tied to, and which one a real clock reads.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/why-microseconds-matter/https://lunartime.org/learn/why-microseconds-matter/A navigation fix is a timing measurement. One microsecond of clock error is 299.79 m of light path, which is why the Moon needs a local time scale.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/news/cgpm-2026-three-time-resolutions/https://lunartime.org/news/cgpm-2026-three-time-resolutions/Six draft resolutions reach the 28th CGPM in October 2026. Three of them are about time: the second, the continuity of UTC, and a lunar time scale.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/news/draft-resolution-d-explained/https://lunartime.org/news/draft-resolution-d-explained/Draft Resolution D asks the 28th CGPM to define an international lunar reference time scale traceable to UTC. What it covers, and what it leaves open.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/news/how-cgpm-voting-works/https://lunartime.org/news/how-cgpm-voting-works/Who sits in the room at the 28th CGPM, how a draft resolution reaches a vote, where lunar time falls in the order of business, and what a vote settles.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/news/what-happens-after-the-vote/https://lunartime.org/news/what-happens-after-the-vote/The 28th CGPM can carry Draft Resolution D or leave it aside. Both outcomes, what each would change, and the deadlines that hold either way.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/frequency-differences-earth-moon-clocks/https://lunartime.org/papers/frequency-differences-earth-moon-clocks/Zhang, Muller and Kopeikin model the frequency difference between Earth and lunar clocks in four steps, and name the Doppler term that hides it.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/international-lunar-reference-frame/https://lunartime.org/papers/international-lunar-reference-frame/Sosnica and colleagues define the Lunar Reference System and give a first realization of the ILRF, with a mean error of 17.6 cm for 2010–2030.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/lte440-lunar-time-ephemeris/https://lunartime.org/papers/lte440-lunar-time-ephemeris/Lu, Yang and Xie publish LTE440, software that converts between Lunar Coordinate Time, TCB and TDB, with accuracy better than 0.15 ns before 2050.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/lunar-reference-timescale/https://lunartime.org/papers/lunar-reference-timescale/Bourgoin, Defraigne and Meynadier review the relativistic effects, put figures on three rate relations, and look for a scale traceable to UTC.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/lunar-time-defraigne-2025/https://lunartime.org/papers/lunar-time-defraigne-2025/Defraigne, Meynadier and Bourgoin compare the candidate reference time scales for the Moon and conclude that TCL can serve without a new scaled scale.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/lunar-time-in-general-relativity/https://lunartime.org/papers/lunar-time-in-general-relativity/Kopeikin and Kaplan derive Lunar Coordinate Time inside general relativity, at nanosecond precision within Earth's Hill sphere of about 1.5 million km.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/novamoon-lunar-reference-station/https://lunartime.org/papers/novamoon-lunar-reference-station/Molli, Fienga, Defraigne and co-authors propose NovaMoon, a geodetic and timing payload for ESA's Argonaut lander, aimed at sub-metre positioning.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/papers/two-birds-with-one-stone/https://lunartime.org/papers/two-birds-with-one-stone/Yang and colleagues propose a time aligned orbit whose clock would read selenoid proper time and convert to Lunar Coordinate Time by a linear step.Mon, 24 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/56-vs-58-microseconds/https://lunartime.org/learn/56-vs-58-microseconds/Both are right. 56.02 µs/day compares clocks on two surfaces; 58.7 µs/day compares Lunar Coordinate Time with Terrestrial Time. The gap is the Moon itself.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/how-long-is-a-day-on-the-moon/https://lunartime.org/learn/how-long-is-a-day-on-the-moon/The Moon turns on its axis in 27.3 Earth days, but sunrise to sunrise at a fixed point takes about 29.5. That gap is why a lunar day needs a definition.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/what-is-coordinated-lunar-time/https://lunartime.org/learn/what-is-coordinated-lunar-time/Coordinated Lunar Time is a proposed time standard for the Moon. It does not exist yet. Here is what has been proposed, by whom, and what is still open.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/why-clocks-run-faster-on-the-moon/https://lunartime.org/learn/why-clocks-run-faster-on-the-moon/Two effects, one number: weaker gravity speeds lunar clocks up, orbital motion slows them down, and the net result is about 56 microseconds per day.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/learn/will-the-moon-have-time-zones/https://lunartime.org/learn/will-the-moon-have-time-zones/The proposals on the table put the whole Moon on one scale, not on zones. Here is what NASA, the IAU and the BIPM actually propose, and what is still open.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/documents/cgpm-28-draft-resolution-d/https://lunartime.org/documents/cgpm-28-draft-resolution-d/Item 17 at the 28th CGPM in Versailles, 13-15 October 2026: the definition of an international lunar reference time scale and its traceability to UTC.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/documents/iau-2024-resolution-ii/https://lunartime.org/documents/iau-2024-resolution-ii/The resolution that created the Lunar Celestial Reference System and Lunar Coordinate Time, and fixed the TCL epoch in TCB at the centre of the Moon.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/documents/iau-2024-resolution-iii/https://lunartime.org/documents/iau-2024-resolution-iii/The companion resolution: it asks international organizations to agree how a lunar reference time scale relates to a lunar coordinate time and to UTC.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/documents/nist-lunar-time-framework-2024/https://lunartime.org/documents/nist-lunar-time-framework-2024/Ashby and Patla's 2024 paper is the source of the 56.02 microseconds per day figure. What it computes, for which clocks, and what it does not claim.Sun, 23 Aug 2026 00:00:00 GMThttps://lunartime.org/documents/ostp-memo-2024/https://lunartime.org/documents/ostp-memo-2024/The White House memorandum that named Coordinated Lunar Time. What it directs, the 58.7 microseconds figure it cites, and the three deadlines it sets.Sun, 23 Aug 2026 00:00:00 GMT