You cannot. The time
element in HTML5 is defined as markup for specific moments or periods or durations of time or for time offsets, not for all concepts related to time.
You can write e.g. <time datetime="2013-04-06T13:53">now</time>
, thereby associating a fixed moment of time with the text content “now”. I don’t see how this could be useful, and the usefulness of the time
element in general is questionable (it looks like markup for markup’s sake), but things like this are all you can do to “define ‘NOW’” with time
.