Trying to help Arjan

date_from_string.rb

# this script proves that no matter how many bytes you leave out of the original string it won't result in a valid date that is in the specified range (within one year)

string = "\x04\x02R\xA6a\xC4M"

bytes = string.unpack("C*")

MIN = Time.new(2013,1,1)
MAX = Time.new(2013,12,31)
# equivalent to:
# string.bytes

def one_item_removed(array)
  array.each_index do |i|
    result = array.dup
    result[i] = nil
    yield result.compact
  end
end

def two_items_removed(array, &block)
  one_item_removed(array) do |a|
    one_item_removed(array, &block)
  end
end

def items_removed(array, n, &block)
  case n
  when 0
    block.call array
  when 1
    one_item_removed(array, &block)
  when 2..array.size
    items_removed(array, n -1) do |x|
      one_item_removed(x, &block)
    end
  else
    raise "what? #{n}"
  end
end

def time(bytes)
  long = bytes.pack("C*").unpack("L*").first
  return "nil" if long.nil?
  t = Time.at long
  in_range = t > MIN && t < MAX
  raise "GEVONDEN!" if in_range
  puts "#{t} #{'<===' if in_range}"
end

puts
puts "original"
puts time(bytes)

puts
puts "1 byte removed"
items_removed(bytes, 1) do |x|
  puts time(x)
end

(2..bytes.size).each do |n|
  puts
  puts "#{n} bytes removed"
  items_removed(bytes, n) do |x|
    puts time(x)
  end
end

I'm quite proud of line 33 :)