They seek to create a common time zone for the Moon: what would change for satellites, robots, and future human bases

The discrepancy in time between Earth and the Moon, though small, can affect the precision of communications and navigation in space missions. (Illustrative image Infobae) When a spacecraft approaches the Moon, a minimal difference in clocks can alter a precision maneuver. That is why, as the United States, Europe, China, Japan and other powers prepare permanent missions, an infrastructure as necessary as a spacecraft or an antenna has emerged: a common lunar timekeeping system. The debate has already reached international scientific institutions and the United States Congress. The issue seems domestic, almost administrative, compared to the challenges of space travel. However, time defines when a mission lifts off, at what instant a satellite transmits data, how an autonomous vehicle positions itself, and what position navigation systems calculate. On Earth, these tasks depend on a network of atomic clocks linked to Coordinated Universal Time, known as UTC. On the Moon, that reference requires adjustments. More than 90 countries are debating the issue at the General Conference on Weights and Measures, being held in Versailles. The meeting puts on the table the creation of a Coordinated Lunar Time, a scale linked to terrestrial UTC, though adapted to the physical conditions of the natural satellite. The goal is for agencies, astronauts, companies and control centers to use the same time frame, even when a mission loses contact with Earth. In parallel, the United States House of Representatives advanced with the Celestial Time Standardization Act, identified as HR 2313. The US Congress is considering a bill to develop a lunar timekeeping system to support future space missions and presence on the Moon. (AP/Ahn Young-joon) The Science, Space and Technology Committee approved the bill on April 29, 2025. The initiative tasks NASA with developing a Coordinated Lunar Time system, or LTC, compatible with the terrestrial standard and prepared for future long-duration missions. The US proposal does not seek to impose a local time similar to Earth's time zones. No one imagines, for now, a lunar "noon" to organize the daily life of a city that does not yet exist. The purpose is much more technical: to create a precise, continuous and shared scale that makes it possible to establish the exact moment of each operation. That foundation will serve to coordinate satellites, landers, robots, communications and human activities. Scientists seek to establish a Coordinated Lunar Time for space exploration, compatible with Coordinated Universal Time (UTC). The challenge arises from a fundamental property of the universe: time does not pass the same everywhere. The theory of general relativity, formulated by Albert Einstein, establishes that gravity affects the passage of clocks. A clock under stronger gravity advances differently from one subjected to weaker gravity. The Moon has less mass than Earth and, therefore, its gravity is also weaker. That difference causes lunar time to advance slightly faster than terrestrial time. The specialists gathered in Versailles estimated an average difference of 58.7 microseconds per day. A microsecond equals one millionth of a second. On a human scale, the gap seems irrelevant: nearly half a century is needed for about one second to accumulate. For a space mission, where signals travel at great speed and positions are calculated with enormous accuracy, the figure demands corrections. The Celestial Time Standardization Act will facilitate coordination between space agencies and private companies on the Moon and other celestial bodies in the future. (NASA/Handout via REUTERS) Navigation systems convert time into distance. If a clock marks an incorrect interval, the program guiding a spacecraft interprets that the signal arrived earlier or later than it actually did. That variation modifies its position calculation. On the ground, the satellites that make up geopositioning systems apply relativistic corrections continuously. Without those adjustments, a phone or a car would accumulate growing errors in its location. The same logic applies to lunar operations, with greater complexity. There is no mature navigation infrastructure there like the one surrounding Earth. Each mission requires coordinating its own devices, relay satellites, ground antennas and equipment located on the surface. If programs use time scales that do not respond to a single criterion, data exchange and shared maneuvers can lose precision. The astronomer Claudio Martínez explained the operational risk in statements to Infobae. "If we use Earth's time to coordinate activity on the Moon there can be significant differences, which when carrying out a specific task, such as the landing of a spacecraft, could cause it to end up hundreds of meters from the landing site due to this temporal lack of coordination," he said. The lunar timekeeping system must be scalable for use on Mars and other celestial bodies, allowing more coherent space exploration. (AP) The dimension of the problem depends on the type of task. A voice communication between astronauts does not require the same precision as an automated descent onto uneven terrain. Nor does an observation camera need it, unlike a vehicle that must dock with an orbital station. But a single standard prevents each space program from adopting incompatible methods and allows combining instruments of different nationalities within the same network. Cheryl Gramling, responsible for lunar position, navigation, timing and standards at NASA headquarters in Washington, illustrated the accumulation of errors with a comparison. "For something traveling at the speed of light, 56 microseconds is enough to travel the distance of approximately 168 soccer fields," she analyzed. The expression does not describe a physical displacement of the spacecraft, but the distance a signal can travel during that interval. The specialist added: "If someone is orbiting the Moon, an observer on Earth who is not compensating for the effects of relativity over the course of a day would think the orbiting astronaut is approximately 168 soccer fields away from where they really are." That gap illustrates why timekeeping is part of safety and navigation, not just of laboratories dedicated to measuring time. Coordinated Lunar Time will be essential for future operations on the Moon, especially for missions under NASA's Artemis program (Image/NASA) The future LTC must maintain a clear link with UTC, the civil and technological reference used on Earth. That connection will allow comparing records from a lunar base with data sent from terrestrial control centers. At the same time, the system must maintain autonomy. If a lunar antenna temporarily loses communication with Earth, its devices cannot stop their clocks or lose the ability to execute scheduled operations. The US law also requires that the model be expandable to other destinations. Mars appears as the next relevant case, although it presents its own conditions of gravity, rotation and distance. The lunar experience could provide technical principles and international agreements for a scenario where several agencies and companies operate beyond Earth's orbit. The central idea is to prevent each mission from building an independent time incompatible with the others. Einstein's general relativity explains why time passes at a different speed on the Moon, which requires a specific timekeeping system for space missions. (NASA) The international debate goes beyond NASA. A time reference for the Moon must be accepted by space agencies, metrology institutes, telecommunications organizations and the private actors planning commercial activity. Cooperation is necessary because one country's satellites can assist another's spacecraft, and because the infrastructure planned for the lunar environment will be shared. Davide Calonico, scientific director of Italy's National Institute of Metrological Research and a member of the expert group, summarized the state of the discussion during the Versailles conference. "We will vote in the coming days. It will be a step forward, and in the coming years the scenario and the reference framework to be used will be defined," he said in statements to the ANSA agency. The delegates also addressed an issue related to the very definition of the second. The current unit depends on a specific energy transition of the cesium atom, measured by atomic clocks. New optical clocks, based on atoms such as strontium or ytterbium, promise superior accuracy. The technological advance is driving a possible formal redefinition before 2030, although the change requires scientific consensus and an orderly transition. The development of a timekeeping system for the Moon would open the door to the creation of commercial standards and infrastructure for a permanent human presence in space. (NASA) "The great ambition is to redefine it by 2030," Calonico explained. The eventual adjustment would affect telecommunications, satellite navigation, quantum research and systems that require high-precision synchronization. It would also influence the design of a Coordinated Lunar Time, because any new extraterrestrial scale must maintain traceability with the basic unit of the International System. Another pending issue is the leap second, an adjustment that compensates for variations in Earth's rotation to keep atomic time close to the duration of the solar day. Computer networks and communication systems question that periodic correction because of the problems it can cause in digital records. The discussion seeks formulas that preserve the continuity of UTC without affecting the precision required by science and civil activities. Before a lunar base has permanent inhabitants, its modules, vehicles and satellites will need to know exactly when to act. The definition of that common clock is advancing in laboratories, congresses and legislative committees. The upcoming agreements will determine whether the exploration of the Moon shares only territory, resources and communications, or also a measure of time designed to function far from Earth.