"EURIBOR": The Euro Interbank Offered Rate. Sponsored by the European Banking Federation (EBF) , EURIBORÂ® is a formal benchmark or reference interest rate since 30 December 1998. It estimates the all-in, simple interest rate (including credit premium and liquidity premium) at which euro denominated interbank term deposits for spot value (T+2) are offered within the euro-zone by one prime bank to another prime bank in the period before 10. 45 CET each business morning. EURIBOR is calculated for periods ranging from one day to one year. It is quoted to three decimal places and on an actual/360 day-count.