I am a native speaker, and have studied english etymology for many years. I have seen the evolution of language over many thousands of years. We have in retrospect, created too many definitions and reasons why things happened in the past, without realizing the modern usage of language. The true aspect of this is that we have become that which we tried to correct... which is misinformed and sticklers. That has become an article of use. For example ¨he is that painter!" while this may seem awkward in many cases, "that" is acting as both an article and a pronoun identifier which recounts a previous conversation or line of text. "the" would have been just as suitably used in the same situation.
Is "now" a "preposition"? I believe that this argument can be resolved in a manner without the otherwise necessarily obligatory thesis / disertation required to dispute the last claim made by curiousdanni. As a linguist and etymologist, I concure that grammar rules from the 1750´s that distinguised that as a demonstrative, but if you look at its role in current times, it can act as a article. If you still don't concur, look at google NGRAM veiwer at the modern usage and you'll see a clear shift in its movement in the last few years. Before you castrate, let's have a look at the data.
Let´s also cite some information about articles:
Every noun must be accompanied by the article, if any, corresponding to its definiteness, and the lack of an article (considered a zero article) itself specifies a certain definiteness.
Study of this approach follows the identity that "that" is being used as a representative numerical identifier.
Articles are usually characterized as either definite or indefinite. A few languages with well-developed systems of articles may distinguish additional subtypes. Within each type, languages may have various forms of each article, according to grammatical attributes such as gender, number, or case, or according to adjacent sounds.( https://en.wikipedia.org/wiki/Article_(grammar) )
Futher research into this aspect of current usage rectifies the nonsesquipedalian incomprehensibilities that are accompanied by the average sesquipedalianismistic person.