A note on terminology
Some existing publications and applications use "Mars Coordinated Time" or "MTC" for mean solar time at the Martian prime meridian. This project labels that rotational time as Airy Mean Time (AMT) and reserves Mars Civil Time (MCT) for the proposed civil time referenced to 30°E in Arabia Terra. Neither MRT nor MCT is currently an adopted international standard.
AMT — Airy Mean Time
Established convention Mean solar time at the Martian prime meridian (0°E, the crater Airy-0). This is the scientific and cartographic reference already used by NASA missions, orbiters, and the IAU longitude system.
MSD = Mars Sol Date, computed from Julian Date using the algorithm published by NASA GISS Mars24 and Allison & McEwen (2000).
MCT — Mars Civil Time
Proposed A civil time referenced to 30°E in Arabia Terra, intended for a future society living on Mars rather than for scientific longitude.
MCT does not replace the Martian prime meridian and does not alter the IAU longitude system. It introduces a separate, human-centered civil layer.
LMST — Local Mean Solar Time
Established convention The local mean solar time at any longitude λ (positive east), derived the same way Earth communities experience different local solar times.
LTST — Local True Solar Time
Established convention The actual position of the sun at a given location, differing from LMST by the equation of time. Sunrise, sunset, and illumination should be computed from LTST and solar altitude — not inferred from LMST clock hours alone.
MRT — Mars Reference Time
Experimental proposal A continuous, non-rotational reference scale intended for future coordination between navigation, computing, communications, and infrastructure — conceptually distinct from solar civil time. MRT is not currently defined with a fixed rate, epoch, or reference potential; see /research for the relativistic literature this proposal draws on, including Areocentric Coordinate Time (TCA).
Summary table
| Scale | What it measures | Status |
|---|---|---|
| AMT | Mean solar time at 0°E (Airy-0) | Established scientific convention |
| MCT | Civil time at 30°E (Arabia Terra) | Proposed, experimental |
| LMST | Local mean solar time at any longitude | Established convention |
| LTST | Local true solar time (actual sun position) | Established convention |
| MRT | Continuous technical reference scale | Experimental proposal, undefined rate/epoch |