Time stamp on manual transactions

I like to use manual transactions to correct certain types of problems in our database - for example if a service outage results in affiliates not getting new customers for a while, I can enter compensating transactions. But without a timestamp, the payouts don't get calculated correctly. I want to be able to enter transactions on the date when they should have occurred, not always right now. If you could add a date/time field to the manual transaction entry fields, that would be great.