DateTime substitution from a string in Ruby/Rails

Imagine that I have this string coming from some external api. The string format is always same including the HTML tags and everything.

"<p>The update time is <strong>Tuesday 04/28/15 08:30 AM PDT</strong>, please disregard the old timing."

How do I extract the DateTime from the string (Tuesday 04/28/15 08:30 AM PDT) and convert it to EST and then wrap it back to string around the <strong> tags?