retrodiction in 2-time

While working on this timetravel bug, I've come to a bit of a better understanding of 2-time, specifically retrodiction in 2-time.

Let us say that when you enter a transaction you can give an effective date, either past or future. One time axis then is the time of entry and the other is the effective date. You could now potentially navigate time along either axis while viewing the state of the system. For example, I might want to view the state of the system as it was yesterday given only yesterday's entries. Or I might want to view the state of the system as it was yesterday given today's entries/corrections as well. And of course, you could view future states too.

The brain tease for me is, how do you implement such a system so that it can scale?