Artistic Rendering Moon Earth. Depositphotos.

Lunar Time: The Puzzle of Timekeeping on the Moon

As space organizations plan to establish a human presence on the Moon, the need for a suitable lunar time zone becomes increasingly pressing. The puzzle of timekeeping on the Moon is complicated by the difference in gravity and speed compared to Earth, leading to a debate among scientists about whether to adhere to Earth time or adopt lunar time. A common reference time for the Moon could greatly simplify communication and navigation for future missions, but developing a functional lunar time system presents a significant challenge.


Neil Armstrong made history on July 21, 1969, by taking a small step for man and a giant leap for mankind on the Moon. However, while the universal standard time on Earth marked the exact moment as 2:56 a.m., the question remains: what time was it really for the astronaut?

At present, the question remains unanswered, but with plans to establish a human presence on the Moon, this may soon change. In a recent meeting in the Netherlands, space organization members from across the globe agreed on the need to establish a suitable lunar time zone – an internationally recognized reference time for the Moon – that future missions can use to facilitate communication and navigation.

Pietro Giordano, a navigation systems engineer at the European Space Agency (ESA), said that a joint international effort is now underway to achieve this. The recent meeting in the Netherlands was organized and led by ESA researchers, but the discussion was extremely collaborative.

Meet LunaNet

The objective is to establish a framework mutually agreed upon called LunaNet, that will provide a common interface for all future lunar missions. It will simplify the way they network, navigate, detect, report, and communicate. Time will play a crucial role in these future operations.


Over the next few years, numerous space agencies and private companies are planning to launch multiple robotic landing modules to the Moon. Moreover, a joint effort by the European Space Agency (ESA), NASA, the Japan Aerospace Exploration Agency (JAXA), and the Canadian Space Agency (CSA) is underway to build a lunar orbit station, named Gateway, which will serve as a launching point for future missions. According to an ESA press release, these missions will not only coexist in the same vicinity of the Moon but will also interact with each other, possibly transmitting communications, conducting joint observations, or rendezvous operations.

Atomic Clocks

Throughout history, all missions to the Moon have relied on Earth’s atomic clocks to monitor their progress, aligning their time in space with the time on their home planet. Essentially, this involves “calling home by radio” and inquiring about the time on Earth while considering the time taken to make the call. An ordinary clock on a spacecraft would not suffice. The gravity and speed on the Moon differ from those on Earth, affecting time differently than the forces closer to our planet.

This practical implication is that if an astronaut on the Moon carried a watch from Earth, it would run faster than normal by tens of microseconds per day. The rate of the watch’s gain depends on whether the astronaut is in orbit or standing on the Moon. It will be challenging to establish a dependable and precise timing system specifically for the Moon under these complex conditions, but it could be more accurate and faster than synchronizing with Earth time.

Lunar or Earth time?

Scientists are currently debating whether to adhere to Earth time or adopt lunar time. The latter would entail creating a functional lunar time system and a common coordinate system for the Moon’s surface, similar to the one we employ on Earth to track orbiting satellites. While this may require more resources and effort, it could lead to a significantly more precise system that could be extended to other planets.


Bernhard Hufenbach, head of strategic planning at the ESA, explained that “the agreed-upon time system will also have to be practical for astronauts.” This presents a significant challenge on a planetary surface where days in the equatorial region last 29.5 Earth days, including fifteen-day lunar frost nights, and the entire Earth appears as a small blue circle in the dark sky. It’s a puzzle that would delight any mathematician. Javier Ventura-Traveset, who coordinates ESA’s contributions to LunaNet, added that “exploration has been a key driver for improving geodetic and timing reference models throughout human history.” This makes it an exciting time to be developing a lunar time system.

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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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