diff --git a/nao-randym/date_converter.rb b/nao-randym/date_converter.rb
new file mode 100644
index 0000000..d594946
--- /dev/null
+++ b/nao-randym/date_converter.rb
@@ -0,0 +1,69 @@
+# encoding: UTF-8
+require 'date'
+a = %w[18730101 19120730 19261225 19890108]
+a << (Time.now+(60*60*24)).strftime('%Y%m%d')
+eras = %w[明治 大正 昭和 平成]
+$date_ranges= {}
+(a.size-1).times do |i|
+  $date_ranges[(Date.parse(a[i])...Date.parse(a[i+1]))] = eras[i]
+end
+
+def convert(input_date)
+
+  output = 'Your date sucks.'
+  date = Date.parse(input_date.gsub!('-', ''))
+  $date_ranges.each do |range, era|
+    if range.include? date
+      nengo = era
+      nengo_year = date.year - range.first.year + 1
+      nengo_year += 5 if era == '明治'
+      output = date.strftime("#{nengo}#{nengo_year}年%-m月%-d日")
+    end
+  end
+  output
+end
+
+require 'test/unit'
+
+class TestFoo < Test::Unit::TestCase
+
+  def test_simple_one
+    ret = convert('2012-10-20')
+    assert_equal('平成24年10月20日', ret)
+  end
+
+  def test_showa_end
+    ret = convert('1989-01-07')
+    assert_equal('昭和64年1月7日', ret)
+  end
+
+  def test_heisei_start
+    ret = convert('1989-01-08')
+    assert_equal('平成1年1月8日', ret)
+  end
+
+  def test_out_of_bounds_max
+    ret = convert((Time.now+(60*60*24)).strftime('%Y-%m-%d'))
+    assert_equal('Your date sucks.', ret)
+  end
+
+  def test_just_in_bounds_max
+    ret = convert(Time.now.strftime('%Y-%m-%d'))
+    assert_not_equal('Your date sucks.', ret)
+  end
+
+  def test_out_of_bounds_min
+    ret = convert('1872-12-31')
+    assert_equal('Your date sucks.', ret)
+  end
+
+  def test_just_in_bounds_min
+    ret = convert('1873-01-01')
+    assert_equal('明治6年1月1日', ret)
+  end
+
+  def test_out_of_bounds_max
+    ret = convert('2030-01-01')
+    assert_equal('Your date sucks.', ret)
+  end
+end