The usage fashion between “contemporary” and “modern” crossed over somewhere in the mid-aughts, though the shifting meaning of “modern” makes a precise diagnosis difficult. (all screenshots via chronicle.nytlabs.com)
new web app created by the research and development wing of the New York Times allows users to create graphs tracing the appearance of individual terms or phrases in the paper over the course of its century-and-a-half history. The graphing tool, called Chronicle, is similar to the Ngram Viewer Google has offered for some time.
Here are some example graphs: