diff --git a/02.calendar/cal.rb b/02.calendar/cal.rb
new file mode 100755
index 0000000000..716f63b17a
--- /dev/null
+++ b/02.calendar/cal.rb
@@ -0,0 +1,41 @@
+#!/usr/bin/env ruby
+
+require "date"
+require "optparse"
+
+options = ARGV.getopts("y:m:")
+year  = (options["y"] || Date.today.year.to_s).to_i
+month = (options["m"] || Date.today.month.to_s).to_i
+
+first_day = Date.new(year, month, 1)
+last_day = Date.new(year, month, -1)
+
+# タイトルを出力
+puts (month.to_s + "月" + " " + year.to_s).center(20)
+
+# 曜日を出力
+puts "日 月 火 水 木 金 土"
+
+# 日を出力
+(first_day..last_day).each do |d|
+  if d.day == 1
+    print d.day.to_s.rjust(2 + first_day.wday * 3)
+    if d.saturday?
+      print "\n"
+    end
+    next
+  end
+
+  if d.saturday?
+    print d.day.to_s.rjust(3) + "\n"
+  elsif d.sunday?
+    print d.day.to_s.rjust(2)
+  else
+    print d.day.to_s.rjust(3)
+  end
+
+  if d == last_day
+    print "\n"
+  end
+end
+