require 'optparse'
require 'date'
OptionParser.accept(DateTime) do |s,|
begin
DateTime.parse(s) if s
rescue ArgumentError
raise OptionParser::InvalidArgument, s
end
end
OptionParser.accept(Date) do |s,|
begin
Date.parse(s) if s
rescue ArgumentError
raise OptionParser::InvalidArgument, s
end
end