There is a reference in the essay that the first definition of “eternal”–in the  3rd edition of the American Heritage Dictionary (copyright 1993)–is “outside of time.” It’s revealed in the book-text that this definition followed scientific evidence (beginning around 1960) that the universe (which was formerly often thought to be “eternal”) began about 13.7 billion years ago, in what was referred to as the “Big Bang.” In the Free Online Dictionary, the first definition is “Being without beginning or end; existing outside of time”; in older dictionaries, a common definition was “time without end”; that certainly includes the eternality feature, but also includes the taken-for-granted aspect that there is a relationship between eternality and the passage of time (particularly because that definition refers only to the “non-end” of time, but ignores the “non-beginning” aspect of time); however, since the “Big Bang” discovery, there’s gradually more and more dictionary- definitions which include the totally “outside of time” aspect of eternality. That gradual change in many dictionaries could take decades more after the previous, lengthy, multi-millenia, concept by humans.