That's also idiotic because we don't put a leading zero in front of 1, 2 or 3 digit years, and neither will future historians put one in front of 4-digit ones - it's just gratuitously annoying.
Charlemagne was crowned in 800 AD, not in 0800 or 00800.
Pompeii was destroyed by the Vesuvius in 79 AD, not 079 or 0079 or 00079.
The battle of the Teutoburg Forest was in 9 AD, not 09, 009, 0009 or 00009.
Also why stop at 5 digits while you're being ridiculous?
I'm happy to expand for others; regardless of my feelings on the matter the Long Now use of a leading zero creates questions and engagement, thus spreading their message under the mantra of "there's no such thing as bad press" | "get the public talking".
It's an Advertising 101 strategy and not at all idiotic save perhaps at the surface of first exposure.
I've been reminded before that comparing hn commentary to reddit or other communities is itself a violation of hn guidelines. You can just upvote/downvote or "tap the sign" by posting the hn guidelines. No need for insinuating the redditization nor twitterization of hn commentary.
Charlemagne was crowned in 800 AD, not in 0800 or 00800.
Pompeii was destroyed by the Vesuvius in 79 AD, not 079 or 0079 or 00079.
The battle of the Teutoburg Forest was in 9 AD, not 09, 009, 0009 or 00009.
Also why stop at 5 digits while you're being ridiculous?