https://twitter.com/hirayasu/status/326664409730670592/photo/1/large

17sai.user.js

// -*- coding: utf-8 -*-
// ==UserScript==
// @name        They are all 17 years old
// @author	HIRATA Yasuyuki <yasu@asuka.net>
// @namespace	http://yasu.asuka.net/
// @version	1.1.0
// @include	http://www.google.tld/search?*
// @include	https://www.google.tld/search?*
// @released	2013-04-23
// @updated     2013-04-30
// ==/UserScript==

(function(){
  var members = {
    "井上喜久子": 17,
    "田村ゆかり": 17,
    "野川さくら": 17,
    "佐藤利奈": 17,
    "堀江由衣": 17,
    "石田燿子": 17,
    "松澤由美": 17,
    "こやまきみこ": 17,
    "池澤春菜": 17,
    "田中敦子": 17,
    "たかはし智秋": 23
  };

  var subjectNodes =
    document.evaluate(
      '//div[contains(concat(" ", normalize-space(@class), " "), " answer_subject ")]',
      document,
      null,
      XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
      null
    ).snapshotItem(0);

  var predicateNodes =
    document.evaluate(
      '//div[contains(concat(" ", normalize-space(@class), " "), " answer_predicate ")]',
      document,
      null,
      XPathResult.ORDERED_NODE_SNAPSHOT_TYPE,
      null
    ).snapshotItem(0);

  if(subjectNodes && predicateNodes) {
    var subjectNode = subjectNodes.childNodes[0];
    var predicateNode = predicateNodes.childNodes[0];
    if(subjectNode.nodeValue.match(/(.*)\s*,\s*年齢/)) {
      var age = members[RegExp.$1];
      if(age && predicateNode.nodeValue.match(/(\d+)年(\d+)月(\d+)日/)) {
        var baseBirthday =
          new Date(
            Number(RegExp.$1) + age,
            Number(RegExp.$2) - 1,
            Number(RegExp.$3)
          );
        var today = Date.now();
        var days = Math.floor((today - baseBirthday)/(60*60*24*1000));
        predicateNode.nodeValue =
	  predicateNode.nodeValue.replace(/^\d+歳/, age + "歳と" + days + "日");
      }
    }
  }
})();