Initial prepaid amount is not prorated

Any idea when code for prorating the initial amount will be added? Or is there a good way to handle it now? I need the initial amount prorated for an annual license.

I was able to write a couple of rules to handle quarterly proration. This will work for now, but still interested in your code.

One question about proration and subsequent license purchases:
If someone has a one-year license that will expire Dec. 31, 2014, but wants to renew the license before the expiration, say on Dec. 12, 2014, how is that handled? Would their license then extend or reset to expire on Dec. 31, 2015? Would the amount be the full one-year license price or, because of proration, be more than the full one-year license price (100% plus a %age for the extra days in December)? Since I am trying to use this for a membership site, I don't want there to be a lapse in licenses and also don't want to charge members extra for renewing early. Or is this a Commerce License Billing question?