actual request-received time?

There are a number of 'layers' a request must pass through before it
actually 'hits' a Rails app (e.g., Apache receives a request, Apache
starts a new thread, new thread processes the request and determines
that it's for a dynamic resource so Apache thread passes it to
Passenger, Passenger passes it to or starts a new Rails process, Rails
app begins processing request. ...) Does anyone know if / how it's
possible to get at the actual time a request hit the first software
layer on the server ?

Thanks,
Bill