Time works differently on the moon – a dilemma that can throw up a few challenges when it comes to timekeeping on the planet’s only natural satellite. It is a problem Congress is seeking to address with the introduction of the Celestial Time Standardization Act (H.R. 2313).

Congresswoman Jennifer McClellan of Virginia introduced the bill last year and recently passed the committee stage, receiving unanimous approval from the U.S. House Science, Space and Technology committee in April 2025. If written into law, it will “require the Administrator of the National Aeronautics and Space Administration to develop celestial time standardization to support future operations and infrastructure on and around the moon and other celestial bodies other than Earth, and for other purposes.” 

Essentially, it will require NASA to create a standard known as Coordinated Lunar Time (LTC) – a celestial equivalent of Coordinated Universal Time (UTC), which is used to regulate clocks and time on Earth and (at present) in space too.

Read More: Here Are 4 Reasons Why We Are Still Going to the Moon

How to Tell Time on the Moon

NASA and other space agencies currently employ a range of timekeeping techniques. This includes Spacecraft Event Time (SCET), which refers to the time an event, such as an observation or engine burn, takes place on the spacecraft. It is typically synced to UTC. Astronauts may also track Mission Elapsed Time (MET) on a separate watch to monitor how much time has passed since the mission began.

However, as the U.S. (and the world) seeks to up the ante on space exploration and even establish a permanent base on the moon, it is becoming increasingly important to establish a consistent and accurate way of measuring time on the moon and beyond.

As the bill states, “the use of Coordinated Universal Time has challenges when used beyond Earth at other celestial bodies, due to relativistic effects.” This refers to the impact of gravity.

On the moon, surface-level gravity is only a sixth of what it is on Earth. This causes clocks to tick a little faster. The difference is infinitesimally small (58 microseconds a day), but because precise timekeeping is essential for navigating space and conducting research, it can pose a significant challenge.

As such, the bill argues, “the United States should lead in developing time standardization for the moon and other celestial bodies other than Earth to support interoperability and safe and sustainable operations.” Doing so “will advance United States leadership in standards setting for global competitiveness, and will benefit other spacefaring countries and entities.”

Preparing for the Future

The bill has overcome the latest hurdle, but there are several more steps to go before it comes into effect. Now, it will be passed to the House, where it will undergo a floor vote. If successful, it will go to the Senate. Only then will it head to the White House to be signed into law. Unlike many policies, the Celestial Time Standardization Act has bipartisan support, so there are high odds of it making it to the finish line.

“We are entering a new era of United States space exploration and have an exciting opportunity to lead on standards that drive global competitiveness. As we pursue increasingly complex activities on the moon and beyond, the need for a celestial time standard will only continue to grow,” Congresswoman McClellan said in a press release last year.

“This will enhance our ability to explore and expand our knowledge of the known universe,” McClellan said.

Read More: Private Lunar Landers So Far Have Seen More Failures Than Successes

Article Sources

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Rosie McCall is a freelance writer living in London. She has covered science and health topics for publications, including IFLScience, Newsweek, and Health.