It’s their version of the Google Books Ngram Viewer, which charts word use over the years in the books they’ve indexed (see The Best Posts To Help Understand Google’s New “Books Ngram Viewer”). The Times, though, indexes word usage in its own history. The image at the top of this post shows the results of my charting “love” and “hate.” It looks like love is winning!
The Chronicle is very easy to use and no registration is required. It, and the Ngram Viewer, can be used with English Language Learners and other students in a number of ways, ranging from just being a fun and simple way for them to play with words to being a tool to correlate certain word usage with political attitudes (as I did in a recent column at Education Week Teacher).