Help measuring response time in Apache

I’m hoping to get some help with time measurements in Apache. I’ve added the %D (response time in milliseconds) token to the common log format but find that it’s only included on GET requests. There’s nothing about this in the Apache documentation.

Does anyone know how to get Apache to respect %D for POST requests, or of any other way of getting this measurement for POST? I’m not in a position to do a custom compile of Apache.