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  2. Planetary hours - Wikipedia

    en.wikipedia.org/wiki/Planetary_hours

    As each day is divided into 24 hours, the first hour of a day is ruled by the planet three places down in the Chaldean order from the planet ruling the first hour of the preceding day; [2] i.e. a day with its first hour ruled by the Sun ("Sunday") is followed by a day with its first hour ruled by the Moon ("Monday"), followed by Mars ("Tuesday ...

  3. Sidereal time - Wikipedia

    en.wikipedia.org/wiki/Sidereal_time

    A mean solar day (what we normally measure as a "day") is the average time between local solar noons ("average" since this varies slightly over a year). Earth makes one rotation around its axis each sidereal day; during that time it moves a short distance (about 1°) along its orbit around the Sun.

  4. Rotation period (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Rotation_period_(astronomy)

    The first one corresponds to the sidereal rotation period (or sidereal day), i.e., the time that the ... Neptune: 0.67125 days [3] 0 d 16 h 6 m 36 ... List of fast ...

  5. Neptune - Wikipedia

    en.wikipedia.org/wiki/Neptune

    Most of the winds on Neptune move in a direction opposite the planet's rotation. [108] The general pattern of winds showed prograde rotation at high latitudes vs. retrograde rotation at lower latitudes. The difference in flow direction is thought to be a "skin effect" and not due to any deeper atmospheric processes. [25]

  6. Equation of time - Wikipedia

    en.wikipedia.org/wiki/Equation_of_time

    where D is the date, counted in days starting at 1 on 1 January (i.e. the days part of the ordinal date in the year). 9 is the approximate number of days from the December solstice to 31 December. A is the angle the Earth would move on its orbit at its average speed from the December solstice to date D.

  7. Calendrical calculation - Wikipedia

    en.wikipedia.org/wiki/Calendrical_calculation

    A calendrical calculation is a calculation concerning calendar dates. Calendrical calculations can be considered an area of applied mathematics. Some examples of calendrical calculations: Converting a Julian or Gregorian calendar date to its Julian day number and vice versa (see § Julian day number calculation within that article for details).

  8. Orbital period - Wikipedia

    en.wikipedia.org/wiki/Orbital_period

    It may also refer to the time it takes a satellite orbiting a planet or moon to complete one orbit. For celestial objects in general, the orbital period is determined by a 360° revolution of one body around its primary, e.g. Earth around the Sun. Periods in astronomy are expressed in units of time, usually hours, days, or years.

  9. List of future astronomical events - Wikipedia

    en.wikipedia.org/wiki/List_of_future...

    On March 14 (which will be February 29 in the Julian calendar), the difference between the Julian calendar and the Gregorian calendar reaches 14 days. Since 14 is divisible by 7, this will be the first time in history since its inception that the Gregorian calendar has the same day of the week for each day of the year as the Julian calendar.