if_in_time_range template tag.

class IfInTimeRangeNode(Node):
    def __init__(self, from_date, to_date, nodelist_true, nodelist_false):
        self.from_date,self.to_date = Variable(from_date),Variable(to_date)
        self.nodelist_true,self.nodelist_false = nodelist_true,nodelist_false
        
    def __repr__(self):
        return '<IfInTimeRangeNode>'

    def render(self, context):
        now = datetime.now()
        try:
            from_date = self.from_date.resolve(context)
        except VariableDoesNotExist:
            from_date = None
        try:
            to_date = self.to_date.resolve(context)
        except VariableDoesNotExist:
            to_date = None
        
        if type(from_date) in (types.StringType, types.UnicodeType, SafeUnicode):
            try:
                from_date = parse_date(from_date)
            except ValueError:
                raise TemplateSyntaxError, "%r: Could not parse from date string." % self

        if type(to_date) in (types.StringType, types.UnicodeType, SafeUnicode):
            try:
                to_date = parse_date(to_date)
            except ValueError:
                raise TemplateSyntaxError, "%r: Could not parse to date string." % self
        
        if from_date < now and to_date >= now:
            return self.nodelist_true.render(context)
        else:
            return self.nodelist_false.render(context)

@register.tag(name="if_in_time_range")
def if_in_time_range(parser, token):
    try:
        tag_name, from_date, to_date = token.split_contents()
    except ValueError:
        raise template.TemplateSyntaxError, "%r tag requires two arguments" % token.contents.split()[0]
    end_tag = 'end'+tag_name
    nodelist_true = parser.parse(('else',end_tag))
    token = parser.next_token()
    if token.contents == 'else':
        nodelist_false = parser.parse((end_tag,))
        parser.delete_first_token()
    else:
        nodelist_false = NodeList()

    return IfInTimeRangeNode(from_date, to_date, nodelist_true, nodelist_false)