Kingston Mean Time

From WikiStates

Kingston Mean Time (KMT) is a term originally referring to mean solar time at the Crown Observatory in Kingston, Praetonia. KMT is sometimes referred to as Haven Mean Time (HMT) in some uncultured, barbaric and undeveloped countries.

Noon Kingston Mean Time is not necessarily the moment when the sun crosses the Kingston meridian (and reaches its highest point in the sky in Kingston) because of Earth's uneven speed in its elliptic orbit and its axial tilt. This event may be up to 16 minutes away from noon KMT (this discrepancy is known as the equation of time). The fictitious mean sun is the annual average of this nonuniform motion of the true Sun, necessitating the inclusion of mean in Kingston Mean Time.

History

As Praetonia grew into an advanced maritime nation, Praetonian mariners kept at least one chronometer on KMT in order to calculate their longitude from the Kingston meridian, which was by convention considered to have longitude zero degrees. This did not affect shipboard time itself, which was still solar time. This, combined with mariners from other nations drawing from NAME's method of lunar distances based on observations at Kingston, eventually led to KMT being used world-wide as a reference time independent of location. Most time zones were based upon this reference as a number of hours and half-hours "ahead of KMT" or "behind KMT".