A calendar drawer for the current month in the terminal

cal.rb

require 'date'

time = Date.today

# print month, year header
puts time.strftime("%B %Y").center(20)

# print th days of the week
puts "Su Mo Tu We Th Fr Sa"

sday = Date.new(time.year, time.month, 1)
days_in_month = (Date.new(time.year, 12, 31) << (12-time.month)).day

print "   " * sday.wday
(1..days_in_month).each do |n|
  print n.to_s.rjust(2)
  sday = sday + 1

  sday.wday == 0 ? print("\n") : print(" ")
end

puts "\n\n"