Time-based shipping...

Is it possible to offer a flat rate shipping option but limit it to orders placed before 2:15pm (or any other time)?

I've had a quick search in the downloads section and the forum, but found nothing yet.

As with any other conditional display with the Shipping Modules ... controlling the $this->enabled is the key ...

If $this->enabled in the Shipping Module does not evaluate as true ... then the Shipping Module does not display ...

This is best done via a function so that you can have a function for the Admin that always evaluates as true for the Modules ... Shipping ... so you can install, remove, configure etc. the Shipping Modules ...

Then, a separate function for the Catalog that evaluates your condition ... in this case, the time ...

Using the Developer's Tool Kit, do a search on:
function zen_get_shipping_enabled

In both the Catalog/Admin ... look to see how these functions are setup as a guide to things that can be done to show/hide the Shipping Module even when the Shipping Module is installed in order to hide or disable it ...