Golden Age vs period of time

Golden Age and period of time both are nouns.

Word	Noun	Adjective	Verb	Adverb
Golden Age	Yes	No	No	No
period of time	Yes	No	No	No

As nouns, period of time is a hypernym of Golden Age; that is, period of time is a word with a broader meaning than Golden Age:

Golden Age: (classical mythology) the first and best age of the world, a time of ideal happiness, prosperity, and innocence; by extension, any flourishing and outstanding period
period of time: an amount of time

Other hypernyms of Golden Age include period, time period.

Golden Age (noun)	period of time (noun)
(classical mythology) the first and best age of the world, a time of ideal happiness, prosperity, and innocence; by extension, any flourishing and outstanding period	an amount of time