From Anstey’s Doctrinal Definitions:
This term refers to the Eternal State (2 Peter 3:12), which exists after time comes to an “end” (1 Cor. 15:24-28). It is also called “the day of eternity” (2 Peter 3:18) and “the ages of ages” (Gal. 1:5; Eph. 2:7; 3:21; 1 Tim. 1:17; 1 Peter 5:11; Rev. 5:13; 22:5).