Quibbles, I got ‘em!
“Russia was still using the Julian Calendar and therefore was running a few days behind”: I’m not sure 13 can be described as “a few.” How about “almost two weeks behind,” or just give the actual number?
“OMG, int. And you thought this initialism didn’t appear until the Al Gore invented the internet.” Is the first “the” unintentional?
Bolshevik, n. and adj. This Russian word literally means “member of the majority,” and was the name taken by Lenin’s supporters in the 1917 revolutions. In later use it would come to be synonymous with Marxist or used for anyone with subversive views.
The general idea is correct, but the dating is wrong. The word goes back (in Russian) to the Second Congress of the Russian Social Democratic Labor Party, held in Brussels and London during August 1903, when Lenin (using his mastery of tactics and infighting) managed to get a majority (bolshinstvo) on a vote about who should be on the editorial board of Iskra and promptly started calling his faction the majority of the party (which they were very far from being), leaving the less hard-nosed faction run by Julius Martov to be stuck with the name “Menshevik” (from menshinstvo, “minority"), a term they were foolish to adopt, since it falsely implied they did not represent the views of most party members. The term “Bolshevik” (большевик) was current in Russian (among the small minority of the population involved in radical politics, of course) from shortly after the Congress. Now, the question is when it came into use in English; I have a hard time believing it was not mentioned once before 1917 considering the interest people in America and the UK took in happenings in Russia, but I’m having trouble finding cites thanks to the horrible metadata at Google Books. It’s true that the term Maximalist was used as a translation in those early days, but I’d think someone would have mentioned the Russian term Bolshevik. At any rate, “the name taken by Lenin’s supporters in the 1917 revolutions” is wrong, whenever the English word is first attested.
Leninist, adj. and n. In 1917, Vladimir Ilyich Ulyanov, better known by his revolutionary nom de guerre Lenin, made his triumphant return to St. Petersburg from exile in Switzerland. Those who followed his particular brand of Marxist thought were quickly labeled Leninists.
Again, the idea is fine but the implication that people were not called “Leninists” until then is incorrect. I have found a cite for the Russian term from 1906. Regardless of whether the English word was used before 1917 (again, I can’t find it in Google Books), the phrasing should be altered to eliminate the implication that the term was first applied after his return from exile.
Soviet, n. and adj, The Russian Soviet Federative Socialist Republic was founded in 1917 in the wake of the October Revolution. The Union of Soviet Socialist Republics would be formed in 1922. The Russian sovet means “council.”
Similar problem with dating: the first Soviet in the relevant sense (after which the Soviet Union was named) was set up in 1905, and the term shouldn’t be tied to the later derivatives “Soviet Socialist Republic” etc. Again, I’ve given up on trying to disentangle Google’s metadata; the term may or may not have been used in English before 1917.