China Solves the Lunar Time Problem

China became the first country to introduce a tool for accurately measuring and comparing time on the Moon and Earth. This solves the long-standing problem of clocks on the Moon running faster than those on Earth.

What Is LTE440?

The system, called LTE440 (Lunar Time Ephemeris), provides lunar timing software for navigation, landings, and future missions.
The technology will eliminate the difference of about 56 microseconds per day that exists due to weak gravity.

Under general relativity, the effect starts imperceptibly but accumulates over time, complicating accurate navigation and time synchronization.

How the System Works

A team from the Purple Mountain Observatory in Nanjing focused on solving the problem. Researchers developed a model accounting for the Moon’s weaker gravity and motion to synchronize lunar time with Earth-based clocks.

Researchers estimate the method stays accurate within tens of nanoseconds, even over intervals of up to 1,000 years.

The model is already integrated into existing software. It allows users to compare lunar and Earth time in one step, without manual or complex calculations. The team aims to make lunar time practical as the number of Moon missions continues to grow.

Harvard astronomer Jonathan McDowell notes that even microsecond deviations quickly accumulate and can disrupt navigation system performance. The effect is especially noticeable when calculations are made minutes ahead.

He said lunar GPS-like systems, especially for precise landings, will soon require addressing these timing issues.

According to him, similar research has been conducted in the United States. However, he is not aware of any American tool as accessible as the one developed by China.

“This shows that China is serious about the Moon and is quite open about sharing its findings,” he emphasized.

Previously, lunar–Earth time differences mattered little because Moon missions were rare.
Engineers used Earth time and made manual corrections for each launch.

But as spacecraft numbers grow and humans return, this method becomes increasingly complex and impractical.

Therefore, in 2024, the International Astronomical Union adopted a system that provides for its own time standard for the Moon. China decided to turn this idea into a working tool for engineers.