Related Clues:

• Existing only in memory
• Like history
• "Back to the Future" destination
• Film noir classic, "Out of the ___"
• One of the tenses
• Background
• Tense time?
• Time you can't relive
• Long-ago period
• Ancient history
• It's behind us
• Time traveler's destination, at least half the time
• It's always behind you
• Tense type
• Not the present or future