Module: Astronoby::Util::Time

Defined in:
lib/astronoby/util/time.rb

Class Method Summary collapse

Class Method Details

.decimal_hour_to_time(date, decimal) ⇒ ::Time

Returns Date and time.

Parameters:

  • date (Date)
  • decimal (Numeric) —

    Hour of the day, in decimal hours

Returns:

  • (::Time) —

    Date and time



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# File 'lib/astronoby/util/time.rb', line 9

def self.decimal_hour_to_time(date, decimal)
  absolute_hour = decimal.abs
  hour = absolute_hour.floor

  unless hour.between?(0, Constants::HOURS_PER_DAY)
    raise(
      IncompatibleArgumentsError,
      "Hour must be between 0 and #{Constants::HOURS_PER_DAY.to_i}, got #{hour}"
    )
  end

  decimal_minute = Constants::MINUTES_PER_HOUR * (absolute_hour - hour)
  absolute_decimal_minute = (
    Constants::MINUTES_PER_HOUR * (absolute_hour - hour)
  ).abs
  minute = decimal_minute.floor
  second = Constants::SECONDS_PER_MINUTE *
    (absolute_decimal_minute - absolute_decimal_minute.floor)

  ::Time.utc(date.year, date.month, date.day, hour, minute, second).round
end

.terrestrial_universal_time_delta(instant) ⇒ Integer, Float

Returns Number of leap seconds for the given instant.

Parameters:

  • instant (Numeric, Time, Date, DateTime)

Returns:

  • (Integer, Float) —

    Number of leap seconds for the given instant



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# File 'lib/astronoby/util/time.rb', line 33

def self.terrestrial_universal_time_delta(instant)
  # Source:
  #  Title: Astronomical Algorithms
  #  Author: Jean Meeus
  #  Edition: 2nd edition
  #  Chapter: 10 - Dynamical Time and Universal Time

  jd = case instant
  when Numeric
    instant
  when ::Time, ::Date, ::DateTime
    Epoch.from_time(instant)
  else
    raise IncompatibleArgumentsError,
      "Expected a Numeric, Time, Date or DateTime object, got #{instant.class}"
  end

  return 69 if jd >= 2457754.5
  return 68 if jd >= 2457204.5
  return 67 if jd >= 2456109.5
  return 66 if jd >= 2454832.5
  return 65 if jd >= 2453736.5
  return 64 if jd >= 2451179.5
  return 63 if jd >= 2450814.5

  theta = ((jd - Epoch::J1900) / 365.25) / 100.0
  if (2415020.5...2450814.5).cover?(jd) # 1900 - 1997
    return -2.44 +
        87.24 * theta +
        815.20 * theta**2 -
        2_637.80 * theta**3 -
        18_756.33 * theta**4 +
        124_906.15 * theta**5 -
        303_191.19 * theta**6 +
        372_919.88 * theta**7 -
        232_424.66 * theta**8 +
        58_353.42 * theta**9
  elsif (2378496.5...2415020.5).cover?(jd) # 1800 - 1899
    return -2.5 +
        228.95 * theta +
        5_218.61 * theta**2 +
        56_282.84 * theta**3 +
        324_011.78 * theta**4 +
        1_061_660.75 * theta**5 +
        2_087_298.89 * theta**6 +
        2_513_807.78 * theta**7 +
        1_818_961.41 * theta**8 +
        727_058.63 * theta**9 +
        123_563.95 * theta**10
  end

  0.0
end