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]
(..) The onset of a migraine headache. If this sounds all too familiar, relief is here at last. Oh no, you bastards. Taggarene. For nearly a decade, doctors have been prescribing... How did you find me here? Taggarene is strong medicine for headaches, toothaches, muscle fatigue, joint pains... (..)1997 The Game