Did they think of 'the 70s' in their particular century like we do?
There's been a fair few threads asking about the same or similar things to you which you might want to take a look at whilst someone can answer your question specifically if the other ones do not:
"What were different decades in the 1800s like?" - Submitted on 25 March 2015: over 100 answers
"How far back does calling decades 50's, 60's, 70's etc go ? Would people in the 18th century casually talk about the 50's like we do?" - Submitted on 17th August 2013, there's a few deleted comments but also a fair few informative ones.
"Did other decades experience cultural categorization (like 90's kids)? In the 1800's, were newspapers referring to "centennials" or discussing how the 1780's generation was different from the 1790's generation?" - Submitted on 29th September 2013, again there's a good amount of informative comments.
"How would you periodize the 1800s in the Western World akin to how the 1900s are generally broken up by decade (e.g. The Roaring Twenties, The Dirty Thirties)?" - Submitted on 15th March 2016
"Is the concept of each decade having its own distinct styles and culture a relatively recent thing, or were decades in past centuries thought of the same way?" - Submitted on 1st January 2016
"Did the 1800s have distinctive decades like the 20th century?" - Submitted on 3rd April 2015
"People of our day and age can easily distinguish cultures via their decade. If we were living in the 1600s, 1700s, or 1800s, could we do the same?" - Submitted on 10th April 2014
"Is the trend of referring to decades as the "[x]ies" a modern thing?" - Submitted on 11th February 2015
I'm sure there will be more and if you'd like to view those click this link on decades