Module: Astronoby::Util::Time

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

Class Method Summary collapse

Class Method Details

.decimal_hour_to_time(date, utc_offset, 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 11

def self.decimal_hour_to_time(date, utc_offset, 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)

  date_in_local_time = ::Time
    .utc(date.year, date.month, date.day, hour, minute, second)
    .getlocal(utc_offset)
    .to_date

  if date_in_local_time < date
    date = date.next_day
  elsif date_in_local_time > date
    date = date.prev_day
  end

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

.terrestrial_universal_time_delta(instant) ⇒ Numeric

Returns Delta T (TT - UT1) in seconds for the given instant.

Parameters:

  • instant (Numeric, Time, Date, DateTime)

Returns:

  • (Numeric) —

    Delta T (TT - UT1) in seconds for the given instant



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# File 'lib/astronoby/util/time.rb', line 46

def self.terrestrial_universal_time_delta(instant)
  case instant
  when Numeric
    IERS::DeltaT.at(jd: instant).delta_t
  when ::Time, ::Date, ::DateTime
    IERS::DeltaT.at(instant).delta_t
  else
    raise IncompatibleArgumentsError,
      "Expected a Numeric, Time, Date or DateTime object, got #{instant.class}"
  end
rescue IERS::OutOfRangeError => e
  if e.available_range
    IERS::DeltaT.at(mjd: e.available_range.end).delta_t
  else
    0
  end
end