The <ins> tag is usually used to highlight inserted text in a HTML document.
Similarly, the <del> tag brings out deleted text.
The datetime attribute can be used to indicate the timestamp of the modification.
<!DOCTYPE html>
<html>
<head>
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<title>HTML tags: <ins> and <del></title>
</head>
<body>
Here is some <del datetime="2014-08-28T16:05:21Z">deleted text</del> while this text here was <ins cite="foo.html">inserted</ins>.
</body>
</html>