The 'decade' of the 1920s runs from January 1, 1920 to December 31, 1929.
There have been a lot of changes during/in/over the past two 'decades'.
a 'decade' of drought [=a drought that lasted 10 years]
(..) "In the decade of the s even the great city of Metropolis... "...was not spared the ravages of the world-wide depression. "In the times of fear and confusion... "...the job of informing the public (..)1978 Superman