Edmar is a Wizard specializing in Evocation. His opposition schools are Enchantment and Abjuration. Having just leveled to 5th he has realized that he keeps wanting to memorize abjuration spells and doesn't even know an illusion so decides to retrain his opposition school.
You may instead retrain your arcane school (including changing to or from a universalist). Doing so replaces your school's bonus spell slots and school powers. This training takes 5 days for every school power you loose from changing schools.
I see several ways this might be accomplished. Some readings might interpret the opposition schools as a power. If so its clearly 5 days of retraining to switch an opposition schools.
On the other hand it might not be so. If not then retraining from and evoker to an evocker with different oppositions would take 0 days. If allowed to do so.
At the same time that smacks of cheese. One could take a hard line and say that oppositions schools must remain the same unless retraining into or out of universalist wizardry. If that were the case then it would take 20 days to achieve the change. Ten days to train to universalist and ten day to train back to evocation.
Personally I favor the first interpretation as it seems to be most in-line with other classes retraining. However this is a PFS character so I thought I would ask and see if I am missing anything or the consensus was otherwise.