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]
(..) Over the past decade, the partnership between the FBI and the Jeffersonian Institution's Forensic Division has resulted in over murder convictions, (..)2016 TvShow: Bones Title: The Movie in the Making Season: 11 Episode 18