reporting date vs reference date

I’ve structured my DHIS by the data the data apply to (I’m calling it reference date) rather than reporting date. For example, cases from 2012 are reported under 2012 even though they were actually reported in 2013. The treatment outcome for those cases is reported in 2014, but they are still added to the database under 2012. This can be a bit confusing for users, because they have to select different datasets and time periods in order to report everything.

DHIS seems to be set up to use reporting date as the basic component of the database. (Or more specifically, the date of the most recently completed time period.) In this sense, treatment outcomes are reported in the same form as cases even though they are for a different cohort. However, I would think there would be a need to capture lag time for each data element which tells you the reference date. In this case 1 year for treatment outcomes.

So besides the question of whether my observations are correct, my question is: What is the best way to set up the database, by reporting date or reference date?