Possible Clues:

• Days gone by, in bygone days
• Bygone time, in bygone time
• Bygone days, in days gone by
• Days long gone, poetically
• Days of yore, of yore
• Antiquity, poetically
• Ancient times, in bygone days
• Relative of yore
• Days of yore, quaintly
• Antiquity, in the past