 specifying the name of the header</dd>
<dt>Returns:</dt>
<dd>a <code>long</code> value representing the date specified in the header expressed as the number of
 milliseconds since January 1, 1970 GMT, or -1 if the named header was not included with the request</dd>
<dt>Throws:</dt>
<dd><code><a href="https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/IllegalArgumentException.html" title="class or interface in java.lang" class="external-link">IllegalArgumentException</a></code> - If the 