From ThresholdRPG Wiki
Acumen Jubilee is one of the many global events that is run on occasion. It provides a chance to earn tons of acumens by slaying monsters or crafting items!
During Acumen Jubilee, any foe or crafting recipe that is of sufficient challenge (generally, one which that you XP) will present a chance to reward you with 1 Acumen. If you are Guild Level 20 or higher, there is also a chance for an ACUMEN CRIT! that will grant you 2-10 Acumens!