Calendars and time
Dynamical Time
Direct answer
Dynamical Time is a general term for uniform time arguments defined for equations of motion rather than by Earth irregular rotation.
Dynamical Time supplies uniform time variables for celestial mechanics.
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At a glance
- Found in
- Calendars & Timekeeping
- Related
- Local Sidereal Time, Barycentric Dynamical Time, Calendar, Julian Date
Dynamical Time supplies uniform time variables for celestial mechanics.
A cycle or timeline schematic for comparing the named timekeeping concept.
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The story behind Dynamical Time
Ephemeris Time and later relativistic coordinate time scales developed as celestial mechanics outgrew mean-solar time.
Why Dynamical Time matters
Orbital calculations require a stable independent variable, while rotational time speeds up and slows down slightly.
Dynamical Time in practice: an example
A planetary ephemeris may be integrated with a barycentric dynamical argument and later converted to UTC for observers.
Where readings of Dynamical Time go wrong
It is a mistake to treat Dynamical Time as one uniquely defined modern clock reading without naming its scale and reference system.
Sources and editorial method
Research references used for this entry include:
- U.S. Naval Observatory Circular 179: The IAU Resolutions on Astronomical Reference Systems, Time Scales, and Earth Rotation Models - Technical reference for TAI, TT, TCG, TCB, TDB, UT1, sidereal time, epochs, and Earth rotation.
- IAU SOFA: Time Scale and Calendar Tools - IAU-standard algorithms and guidance for civil calendars, Julian dates, and seven recognized astronomical time scales.
- Source
- The Great Almanac Dictionary
- Category
- Calendars & Timekeeping
- Last updated
- 2026-09-26
Name the dynamical scale
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More in Calendars & Timekeeping
- Greenwich Mean Time
- Julian Calendar
- Lunar Calendar
- Proleptic Julian Calendar
- Synodic Month
- Week Number
- Common Era
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Common questions
What is dynamical time?
Dynamical Time is a general term for uniform time arguments defined for equations of motion rather than by Earth irregular rotation.
What do people get wrong about dynamical time?
It is a mistake to treat Dynamical Time as one uniquely defined modern clock reading without naming its scale and reference system.
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