1 files changed, 219 insertions, 0 deletions
diff --git a/lib/date2.rb b/lib/date2.rb
new file mode 100644
index 0000000000..50c2ccfbd9
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+++ b/lib/date2.rb
@@ -0,0 +1,219 @@
+# date.rb: Written by Tadayoshi Funaba 1998
+# $Id: date.rb,v 1.4 1998/06/01 12:52:33 tadf Exp $
+
+class Date
+
+  include Comparable
+
+  MONTHNAMES = [ '', 'January', 'February', 'March', 'April', 'May', 'June',
+    'July', 'August', 'September', 'October', 'November', 'December' ]
+
+  DAYNAMES = [ 'Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday',
+    'Friday', 'Saturday' ]
+
+  ITALY   = 2299161 # Oct 15, 1582
+  ENGLAND = 2361222 # Sept 14, 1752
+
+  def Date.civil_to_jd(y, m, d, gs = true)
+    if m <= 2 then
+      y -= 1
+      m += 12
+    end
+    a = (y / 100).to_i
+    b = 2 - a + (a / 4).to_i
+    jd = (365.25 * (y + 4716)).to_i +
+      (30.6001 * (m + 1)).to_i +
+      d + b - 1524
+    unless
+      (if gs.kind_of? Numeric then jd >= gs else gs end) then
+      jd -= b
+    end
+    jd
+  end
+
+  def Date.jd_to_civil(jd, gs = true)
+    unless
+      (if gs.kind_of? Numeric then jd >= gs else gs end) then
+      a = jd
+    else
+      x = ((jd - 1867216.25) / 36524.25).to_i
+      a = jd + 1 + x - (x / 4).to_i
+    end
+    b = a + 1524
+    c = ((b - 122.1) / 365.25).to_i
+    d = (365.25 * c).to_i
+    e = ((b - d) / 30.6001).to_i
+    dom = b - d - (30.6001 * e).to_i
+    if e <= 13 then
+      m = e - 1
+      y = c - 4716
+    else
+      m = e - 13
+      y = c - 4715
+    end
+    return y, m, dom
+  end
+
+  def Date.mjd_to_jd(mjd)
+    mjd + 2400000.5
+  end
+
+  def Date.jd_to_mjd(jd)
+    jd - 2400000.5
+  end
+
+  def Date.tjd_to_jd(tjd)
+    tjd + 2440000.5
+  end
+
+  def Date.jd_to_tjd(jd)
+    jd - 2440000.5
+  end
+
+  def Date.julian_leap? (y)
+    y % 4 == 0
+  end
+
+  def Date.gregorian_leap? (y)
+    y % 4 == 0 and y % 100 != 0 or y % 400 == 0
+  end
+
+  def Date.leap? (y)
+    Date.gregorian_leap?(y)
+  end
+
+  def initialize(jd = 0, gs = ITALY)
+    @jd, @gs = jd, gs
+  end
+
+  def Date.exist? (y, m, d, gs = true)
+    jd = Date.civil_to_jd(y, m, d, gs)
+    if [y, m, d] == Date.jd_to_civil(jd, gs) then
+      jd
+    end
+  end
+
+  def Date.new3(y = -4712, m = 1, d = 1, gs = ITALY)
+    unless jd = Date.exist?(y, m, d, gs) then
+      fail ArgumentError, 'invalid date'
+    end
+    Date.new(jd, gs)
+  end
+
+  def Date.today(gs = ITALY)
+    Date.new(Date.civil_to_jd(*(Time.now.to_a[3..5].reverse << gs)), gs)
+  end
+
+  def jd
+    @jd
+  end
+
+  def mjd
+    def self.mjd; @mjd end
+    @mjd = Date.jd_to_mjd(@jd)
+  end
+
+  def tjd
+    def self.tjd; @tjd end
+    @tjd = Date.jd_to_tjd(@jd)
+  end
+
+  def civil
+    def self.year; @year end
+    def self.mon; @mon end
+    def self.mday; @mday end
+    @year, @mon, @mday = Date.jd_to_civil(@jd, @gs)
+  end
+
+  private :civil
+
+  def year
+    civil
+    @year
+  end
+
+  def yday
+    def self.yday; @yday end
+    ns = if @gs.kind_of? Numeric then @jd >= @gs else @gs end
+    jd = Date.civil_to_jd(year - 1, 12, 31, ns)
+    @yday = @jd - jd
+  end
+
+  def mon
+    civil
+    @mon
+  end
+
+  def mday
+    civil
+    @mday
+  end
+
+  def wday
+    def self.wday; @wday end
+    @wday = (@jd + 1) % 7
+  end
+
+  def leap?
+    def self.leap?; @leap_p end
+    ns = if @gs.kind_of? Numeric then @jd >= @gs else @gs end
+    jd = Date.civil_to_jd(year, 2, 28, ns)
+    @leap_p = Date.jd_to_civil(jd + 1, ns)[1] == 2
+  end
+
+  def + (other)
+    if other.kind_of? Numeric then
+      return Date.new(@jd + other, @gs)
+    end
+    fail TypeError, 'expected numeric'
+  end
+
+  def - (other)
+    if other.kind_of? Numeric then
+      return Date.new(@jd - other, @gs)
+    elsif other.kind_of? Date then
+      return @jd - other.jd
+    end
+    fail TypeError, 'expected numeric or date'
+  end
+
+  def <=> (other)
+    if other.kind_of? Numeric then
+      return @jd <=> other
+    elsif other.kind_of? Date then
+      return @jd <=> other.jd
+    end
+    fail TypeError, 'expected numeric or date'
+  end
+
+  def downto(min)
+    @jd.downto(min.jd) do |jd|
+      yield Date.new(jd, @gs)
+    end
+  end
+
+  def upto(max)
+    @jd.upto(max.jd) do |jd|
+      yield Date.new(jd, @gs)
+    end
+  end
+
+  def step(max, step)
+    @jd.step(max.jd, step) do |jd|
+      yield Date.new(jd, @gs)
+    end
+  end
+
+  def eql? (other)
+    self == other
+  end
+
+  def hash
+    @jd
+  end
+
+  def to_s
+    format('%04d-%02d-%02d', year, mon, mday)
+  end
+
+end