Ruby script to verify of converting Julian Day to Gregorian Calendar.

verify_jd2gc.rb

#! /usr/local/bin/ruby
# coding: utf-8
#=ユリウス日 -> グレゴリオ暦 変換の検証(UTC ベース)
#
#   1. 一旦、グレゴリオ暦 -> ユリウス日 の変換。（by フリーゲルの公式
#   2. そのユリウス日を２種の計算式でグレゴリオ暦に変換。
#   3. ２種の計算式で算出した結果が等しいかチェック。
#
# date          name            version
# 2016.06.14    mk-mode.com     1.00 新規作成
#
# Copyright(C) 2016 mk-mode.com All Rights Reserved.
#---------------------------------------------------------------------------------

class ExConvJdGc
  CHECKS = [
    [1999, 12, 31, 23, 59, 59],
    [2000,  1,  1,  0,  0,  0],
    [2016,  6, 14,  0,  0,  0],
    [2016,  6, 14, 11, 59, 59],
    [2016,  6, 14, 12,  0,  0],
    [2016,  6, 14, 23, 59, 59],
    [2016,  2, 28,  0,  0,  0],
    [2016,  2, 28, 11, 59, 59],
    [2016,  2, 28, 12,  0,  0],
    [2016,  2, 28, 23, 59, 59],
    [2016,  2, 29,  0,  0,  0],
    [2016,  2, 29, 11, 59, 59],
    [2016,  2, 29, 12,  0,  0],
    [2016,  2, 29, 23, 59, 59],
    [2016,  3,  1,  0,  0,  0]
  ]

  def run
    begin
      CHECKS.each do |dt|
        str = sprintf("* GC: %04d-%02d-%02d %02d:%02d:%02dUTC\n", *dt)
        jd = gc2jd(*dt)
        str << "  -> JD: #{jd}\n"
        gc_1, gc_2 = jd2gc1(jd), jd2gc2(jd)
        str << "  -> GC: #{gc_1}, #{gc_2}"
        str << " (NOT MATCH!)" unless gc_1 == gc_2
        puts str
      end
    rescue => e
    end
  end

  #=========================================================================
  # グレゴリオ暦 -> ユリウス日(JD)
  #
  # * フリーゲルの公式を使用する
  #     JD = int(365.25 * year)
  #        + int(year / 400)
  #        - int(year / 100)
  #        + int(30.59 * (month - 2))
  #        + day
  #        + 1721088.5
  #   ※上記の int(x) は厳密には、x を超えない最大の整数
  #   ※正子を整数とする JDN を求めるなら、 1721088.5 を 1721089 に置き換える
  #   ※修正ユリウス日 MJDを求めるなら + 1721088.5 を - 678912 に置き換える。
  #
  # @param:  year
  # @param:  month
  # @param:  day
  # @param:  hour
  # @param:  minute
  # @param:  second
  # @return: JD(Julian Day)
  #=========================================================================
  def gc2jd(year, month, day, hour = 0, min = 0, sec = 0)
    # 1月,2月は前年の13月,14月とする
    if month < 3
      year  -= 1
      month += 12
    end
    # 日付(整数)部分計算
    jd  = (365.25 * year).truncate \
        + (year / 400.0).truncate \
        - (year / 100.0).truncate \
        + (30.59 * (month - 2)).truncate \
        + day \
        + 1721088.5
    # 時間(小数)部分計算
    t  = (hour + min / 60.0 + sec / 3600.0) / 24.0
    return jd + t
  rescue => e
    raise
  end

  #=========================================================================
  # ユリウス日(JD) -> グレゴリオ暦 (Ver.1)
  #
  # * JD = JD + 0.5
  #   a = int(jd + 68569)
  #   b = int(a / 36524.25)
  #   c = a - int(36524.25 * b + 0.75)
  #   d = int((c + 1) / 365.2425)
  #   e = c - int(365.25 * d) + 31
  #   f = int(int(e) / 30.59)
  #   g = int(f.truncate / 11.0)
  #   year  = 100 * (b - 49) + d + g
  #   month = f - 12 * g + 2
  #   day   = e - (30.59 * f).truncate
  #   (hour, min, sec は 小数点以下の端数を処理するだけ)
  #
  # @param:  JD
  # @return: "YYYY-MM-DD HH:MM:SS"
  #=========================================================================
  def jd2gc1(jd)
    # 年月日
    jd += 0.5
    a = (jd + 68569).truncate
    b = (a / 36524.25).truncate
    c = a - (36524.25 * b + 0.75).truncate
    d = ((c + 1) / 365.2425).truncate
    e = c - (365.25 * d).truncate + 31
    f = (e.truncate / 30.59).truncate
    g = (f.truncate / 11.0).truncate
    year  = 100 * (b - 49) + d + g
    month = f - 12 * g + 2
    day   = e - (30.59 * f).truncate
    # 2月30日の補正
    if month == 2 && day > 28
      if year % 4 == 0 && year % 100 != 0 || year % 400 == 0
        day = 29
      else
        day = 28
      end
    end
    # 時分秒
    tm = 86400 * (jd - jd.truncate)
    hour = (tm / 3600.0).truncate
    min  = ((tm - 3600 * hour) / 60.0).truncate
    sec  = (tm - 3600 * hour - 60 * min).truncate
    return Time.new(year, month, day, hour, min, sec).strftime("%Y-%m-%d %H:%M:%SUTC")
  rescue => e
    raise
  end

  #=========================================================================
  # ユリウス日(JD) -> グレゴリオ暦 (Ver.2)
  #
  # * JD = JD + 0.5
  #   a = JD + 32044
  #   b = int((4 * a + 3) / 146097)
  #   c = a - int(146097 * b / 4)
  #   d = int((4 * c + 3) / 1461)
  #   e = c - int(1461 * d / 4)
  #   m = int((5 * e + 2) / 153)
  #   year  = 100 * b + d - 4800 + int(m / 10)
  #   month = m + 3 - 12 * int(m / 10)
  #   day   = e - int((153 * m + 2) / 5) + 1
  #   (hour, min, sec は 小数点以下の端数を処理するだけ)
  #
  # @param:  JD
  # @return: "YYYY-MM-DD HH:MM:SS"
  #=========================================================================
  def jd2gc2(jd)
    jd += 0.5
    # 年月日
    a = (jd + 32044).truncate
    b = ((4 * a + 3) / 146097.0).truncate
    c = a - (146097 * b / 4.0).truncate
    d = ((4 * c + 3) / 1461.0).truncate
    e = c - (1461 * d / 4.0).truncate
    m = ((5 * e + 2) / 153.0).truncate
    year  = 100 * b + d - 4800 + (m / 10.0).truncate
    month = m + 3 - 12 * (m / 10.0).truncate
    day   = e - ((153 * m + 2) / 5.0).truncate + 1
    # 2月30日の補正
    if month == 2 && day > 28
      if year % 4 == 0 && year % 100 != 0 || year % 400 == 0
        day = 29
      else
        day = 28
      end
    end
    # 時分秒
    t = 86400 * (jd - jd.truncate)
    hour = (t / 3600.0).truncate
    min  = ((t - 3600 * hour) / 60.0).truncate
    sec  = (t - 3600 * hour - 60 * min).truncate
    return Time.new(year, month, day, hour, min, sec).strftime("%Y-%m-%d %H:%M:%SUTC")
  rescue => e
    raise
  end
end

ExConvJdGc.new.run if __FILE__ == $0