As humanity prepares to return to the Moon with the Artemis program, one critical challenge has emerged that most people never think about: what time is it on the Moon? On April 2, 2024, the White House Office of Science and Technology Policy (OSTP) directed NASA to establish a unified lunar time standard called Coordinated Lunar Time, or LTC, by the end of 2026.
Why the Moon Needs Its Own Time
On Earth, we rely on Coordinated Universal Time (UTC), which is maintained by a network of over 400 atomic clocks worldwide. GPS satellites, financial systems, power grids, and the internet all depend on precise synchronization with UTC.
The Moon presents a unique problem. Due to its weaker gravitational field, clocks on the lunar surface tick approximately 56.02 microseconds faster per Earth day than identical clocks on Earth. This effect — predicted by Einstein's general theory of relativity — means that a simple relay of Earth time to the Moon would slowly drift out of sync with local lunar clocks.
Over the course of a single day, 56 microseconds may seem negligible. But for navigation systems, that drift translates to position errors of about 16 meters per day. Over a month, errors would reach nearly 500 meters — enough to make precision landings, rover navigation, and communication relay timing unreliable.
How LTC Will Work
Coordinated Lunar Time will be built on the same principles as UTC but adapted for the lunar environment. The plan involves placing a network of atomic clocks on the Moon's surface and in lunar orbit. These clocks will be used to compute a weighted average that defines the official lunar time.
LTC will maintain a fixed, well-defined relationship with UTC so that time can be seamlessly converted between Earth and Moon. The key difference is that LTC will account for the relativistic offset — the cumulative drift that makes lunar clocks run faster.
The National Institute of Standards and Technology (NIST) published a technical framework in August 2024 describing the mathematical model for deriving lunar time from relativistic corrections to UTC.
The International Effort
Lunar timekeeping is not just a NASA project. The United Nations International Committee on Global Navigation Satellite Systems (ICG) established a dedicated working group in 2024 to standardize lunar timing internationally. The Artemis Accords — signed by over 50 nations — recognize the need for interoperable systems, and a shared time reference is foundational to that goal.
The European Space Agency (ESA) has also been studying lunar timekeeping as part of its Moonlight initiative, which aims to provide communication and navigation services around the Moon.
What LTC Means for the Future
A standardized lunar time will enable precision navigation for landers and rovers, reliable communication scheduling between Earth and the Moon, coordination between missions from different space agencies, and eventually a foundation for timekeeping on Mars and beyond.
The simulated Coordinated Lunar Time shown on moontimenow.com uses the published drift rate of +56.02 microseconds per day, accumulated from the J2000.0 epoch, to approximate what an official LTC clock would read today.