Word or phrase for 'Past glory'

Solution 1:

Halcyon comes to mind: see Merriam-Webster

1a : characterized by happiness, great success, and prosperity : golden —often used to describe an idyllic time in the past that is remembered as better than today the halcyon days of youth

Sample Usage: Economic Recovery: Lessons from the Post-World War II Period

The hardships of the previous fifteen years of war and depression were replaced by rising living standards, increased opportunities, and a newly emerging American culture confident of its future and place in the world. It is not surprising that politicians of all stripes harken back to those halcyon days to make a case for their agendas. (emphasis mine)