class Chronic::Tag

they match specific criteria.
Tokens are tagged with subclassed instances of this class when

def initialize(type)

type - The Symbol type of this tag. 
def initialize(type)
  @type = type
end

def scan_for(token, klass, items={}) 

def scan_for(token, klass, items={})
  case items
  when Regexp
    return klass.new(token.word) if items =~ token.word
  when Hash
    items.each do |item, symbol|
      return klass.new(symbol) if item =~ token.word
    end
  end
  nil
end

def start=(time)

time - Set the start Time for this Tag. 
def start=(time)
  @now = time
end