Names of political or cultural periods or events are capitalized in their original connotations but should be in lower case when used in a generic (general) sense.
The arts and sciences flourished during the Renaissance. [Referring specifically to the period of cultural movement called Renaissance in Italy, hence capital]
There are lots of talks on the media these days on the oil renaissance of Texas. [Referring to renaissance in general terms, to mean ‘boom,’ hence lower cased] Here’s an example: http://finance.yahoo.com/video/oil-renaissance-texas-180100936.html
Emperor Akbar’s reign is known as the Golden Age of Mughal rule in India because of obvious reasons.
Jazz music has experienced several golden ages.
He served in the First World War.
During the world wars, with more women going out to work, the demand for day cares increased.
Do not capitalize adjectives preceding the names of nations/political entities.
This essay will discuss the economic structure of imperial Britain.
This essay will discuss the economic structure of Imperial Britain.