Anytime they increase XP/TP gains or boost Drop Rares, usually over a weekend or Holiday period, it is the Taborean Academy. Typically the boost is +100% XP gain from Quests and Combat, with +250% TP gain from Quests and Combat. For some special "weekends", such as over the Christmas break, the boost may be as much as double that.
See the client updater/launcher splash screen for specifics. This event usually starts at 3pm (Pacific Time) and ends at 1 minute to midnight (Pacific Time).