| time measured by the orbital movements of the earth, the moon, and the planets. |
| ephemeris time n. A highly accurate astronomical system for the measurement of time based on the period of Earth's orbit, but in practice relying on lunar observations and an accurate lunar ephemeris. |
| ephemeris time
A highly accurate astronomical system for the measurement of time based in theory on the period of Earth's orbit, but in practice relying on lunar observations and an accurate lunar ephemeris so as to not be subject to the irregularities of Earth's rotation. The year 1900 CE is considered a standard year, containing 31,556,925.9747 seconds of ephemeris time. |