My calender

02.calendar/my_calender.rb

@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require 'optparse'
+require 'date'
+parameters = ARGV.getopts('y:', 'm:')
+
+def print_calender(first_day, last_day)
+  first_line_indent = first_day.wday
+
+  print "#{first_day.strftime('%B')} #{first_day.year}".center(23)
+  puts
+
+  %w[Su Mo Tu We Th Fr Sa].each do |x|
+    print x.rjust(3)
+  end
+  puts
+
+  first_line_indent.times do
+    print '   '
+  end
+
+  (first_day..last_day).each do |x|
+    if x == Date.today
+      print "\e[7m#{x.day.to_s.rjust(3)}\e[0m"
+    else
+      print x.day.to_s.rjust(3)
+    end
+    puts if x.saturday?
+  end
+  puts
+end
+
+def validate_month(month)
+  return unless month.to_i < 1 || month.to_i > 12
+
+  print "cal: #{month} is neither a month number (1..12) nor a name"
+  puts
+  exit
+end
+
+input_year = parameters['y']
+input_month = parameters['m']
+validate_month(input_month) if input_month
+today = Date.today
+
+year = input_year || today.year
+month = input_month || today.month
+
+first_day = Date.new(year.to_i, month.to_i, 1)
+last_day = Date.new(year.to_i, month.to_i, -1)
+
+print_calender(first_day, last_day)