solar time
Noun
Meaning
solar time (uncountable)
(astronomy) The local time based on a solar day—the mean time between successive noons.
Synonyms
Examples
Also on the day of an equinox, the Sun rises everywhere on Earth (except at the poles) at about 06:00 and sets at about 18:00 (local solar time).
Both solar time and sidereal time make use of the regularity of Earth's rotation about its polar axis, solar time following the sun while sidereal time roughly follows the stars.
Definition Until 1972 all time zones were specified as an offset from Greenwich Mean Time (GMT), which was the mean solar time at the meridian passing through the Royal Observatory in Greenwich, London.
De Sitter offered a correction to be applied to the mean solar time given by the Earth's rotation to get uniform time.
History Early timekeeping Before clocks were first invented, it was common practice to mark the time of day with apparent solar time (also called "true" solar time) – for example, the time on a sundial – which was typically different for every settlement.
In this way, local times will continue to stay close to mean solar time and the effects of variations in Earth's rotation rate will be confined to simple step changes relative to the uniform time scale ( International Atomic Time or TAI).