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  2. Julian year (astronomy) - Wikipedia

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

    In astronomy, a Julian year (symbol: a or a j) is a unit of measurement of time defined as exactly 365.25 days of 86 400 SI seconds each. [1] [2] [3] [4] The length ...

  3. Year - Wikipedia

    en.wikipedia.org/wiki/Year

    The Julian year, as used in astronomy and other sciences, is a time unit defined as exactly 365.25 days of 86 400 SI seconds each ("ephemeris days"). This is the normal meaning of the unit "year" used in various scientific contexts.

  4. Astronomical system of units - Wikipedia

    en.wikipedia.org/wiki/Astronomical_system_of_units

    The astronomical unit of time is the day, defined as 86 400 seconds. 365.25 days make up one Julian year. [1] The symbol D is used in astronomy to refer to this unit. Astronomical unit of mass

  5. Orders of magnitude (time) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(time)

    Because of this, the table below does not include weeks, months, and years. Instead, the table uses the annum or astronomical Julian year (365.25 days of 86,400 seconds), denoted with the symbol a. Its definition is based on the average length of a year according to the Julian calendar, which has one leap year every four years.

  6. Julian day - Wikipedia

    en.wikipedia.org/wiki/Julian_day

    The Julian period is a chronological interval of 7980 years, derived from three multi-year cycles: the Indiction, Solar, and Lunar cycles. The last year that was simultaneously the beginning of all three cycles was 4713 BC (−4712), [2] so that is year 1 of the current Julian period, making AD 2025 year 6738 of that Period. The next Julian ...

  7. Terrestrial Time - Wikipedia

    en.wikipedia.org/wiki/Terrestrial_Time

    The Julian Date is a linear transformation of the raw count of ... ΔT is somewhat unpredictable, with 10-year extrapolations diverging by 2-3 seconds from the ...

  8. Barycentric Dynamical Time - Wikipedia

    en.wikipedia.org/wiki/Barycentric_Dynamical_Time

    As of the beginning of 2011, the difference between TDB and TCB is about 16.6 seconds. TDB = TCB − L B ×(JD TCB − T 0 )×86400 + TDB 0 where L B = 1.550519768 × 10 −8 , TDB 0 = −6.55 × 10 −5 s, T 0 = 2443144.5003725, and JD TCB is the TCB Julian date (that is, a quantity which was equal to T 0 on 1977 January 1 00:00:00 TAI at the ...

  9. Portal:Years/Intro - Wikipedia

    en.wikipedia.org/wiki/Portal:Years/Intro

    In astronomy, the Julian year is a unit of time, defined as 365.25 days of 86 400 SI seconds each (no leap seconds). There is no universally accepted symbol for the year as a unit of time. The International System of Units does not propose one. A common abbreviation in international use is a (for Latin annus), in English also y or yr.