Metric time is the measure of time interval using the metric system, which defines the second as the base unit of time, and multiple and submultiple units formed with metric prefixes, such as kiloseconds and milliseconds. It does not define the time of day, as this is defined by various time ...
Sidereal time is a time-keeping system astronomers use to keep track of the direction to point their telescopes to view a given star in the night sky. Briefly, sidereal time is a time scale that is based on the Earth's rate of rotation measured relative to the fixed stars.
Solar time is a reckoning of the passage of time based on the Sun's position in the sky. The fundamental unit of solar time is the day. Two types of solar time are apparent solar time and mean solar time.
Daylight saving time or summer time is the practice of advancing clocks during the lighter months so that evenings have more daylight and mornings have less. Typically clocks are adjusted forward one hour near the start of spring and are adjusted backward in the autumn.
The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. and p.m.. The 24 hour/day cycle starts at 12 a.m., runs through 12 noon and at the end of the day moves immediately to 12 a.m. of the next day.
A time zone is a region that has a uniform standard time for legal, commercial, and social purposes. It is convenient for areas in close commercial or other communication to keep the same time, so time zones tend to follow the boundaries of countries and their subdivisions.
A system of measurement is a set of units of measurement which can be used to specify anything which can be measured and were historically important, regulated and defined because of trade and internal commerce.
A week is a time unit equal to seven days. It is the standard time period used for cycles of work days and rest days in most parts of the world.
