<p>I'd like to know if Flash/AS3 has any nice way to convert an AS3 'Date' object to/from rfc-850 timestamp format (as used by HTTP date and last-modified).</p>

<p>This question is very similar to <a href="https://stackoverflow.com/questions/17017/how-do-i-parse-and-convert-datetimes-to-the-rfc-3339-date-time-format">this question about rfc 3339</a>, except it's specific to AS3 and rfc-850.</p>

<p>RFC-850 is like: <code>Thu, 09 Oct 2008 01:09:43 GMT</code></p>

The
as3corelib
libraries have DateUtil.toRFC822() and DateUtil.parseRFC822() methods (among others). Don't know if these are exactly what you are looking for.
The specific docs for the DateUtil class is here:
http://as3corelib.googlecode.com/svn/trunk/docs/com/adobe/utils/DateUtil.html