Override/set Current-Time for rlm_logintime testing

I'm working on using rlm_logintime to enforce time of day logins for certain users. I'm also building some radclient packets that I can use to test different time boundaries to make sure my policies are correct. However, logintime looks like it's always using the packet arrival time to do its calculations (understandably; there's no other reliable source). Is there any way to override the packet arrival time, through an attribute or function? I tried setting Packet-Original-Timestamp with no luck. I also tried setting Current-Time, but that looks like a kind of virtual attribute that can be checked (against simple time strings), but not printed or assigned directly. Thanks for any clarification, Jason