So in the present many people refer to the 1980’s as just “the 80’s” and the 1990’s as “the 90’s”. Has this always been a trend to refer to the past few decades in this way or is it a relatively new thing?
You may have an interest in previous threads like this: https://www.reddit.com/r/AskHistorians/comments/7av2su/when_did_people_start_calling_decades_the_s_such/
(Variations on this question get asked relatively frequently.)
But the short answer is: "Yes". People in the early 1900s would have referred to decades in the 19th century as "the sixties" or "the nineties", etc.
If I recall correctly I, personally, most recently came across this the other week while leafing through Lord Cromer's 1908 Modern Egypt where he refers to "the sixties."