Financing a large purchase over time

#!/usr/bin/ruby            

require 'Date'

print "How much to save? "
save = gets.chomp.gsub('$', '').to_f
puts ''

print "When do you need it? (2009 12 25) "
(year, month, day) = gets.chomp.split(/\s+/).map{|m| m.to_i}

d = Date.new(year, month, day)
weeks = ((d - Date.today) / 7).to_i

amount = sprintf("%.02f", save / weeks)

puts ''
print "To save $#{'%.02f' % save} by #{month}/#{day}/#{year} (#{weeks} weeks),"
print " you need to save $#{amount} / week.\n"