I think it's part of the account creation date, not all accounts have a phone number.

That’s the time zone offset and year of the “created at” timestamps.

That’s just a date value, “+0000” means UTC and 2009 is the year. If the value is in the phone field, might be a glitch or hidden value stored in the phone field that has a meaning that is undocumented; for example that the account was created prior to the phone field being added, though that seems unlikely, since my understanding is Twitter started out as phone-based.

No the phone requirement came way later.

You used to be able to sign up with just an email address then they started forcing phone number verification by lying and saying they caught your account acting like a bot so you needed to verify you’re human using phone number (you got the message even if you did nothing or just followed a few people, total lie)

How did twitter start as an sms system without requiring phone numbers?

They pivoted away from being an SMS system and that became a legacy part of it, that still worked but wasn't essential.

The part where Twitter was SMS only is like a footnote in its history.

Point is that generally speaking databases rarely delete fields once added, especially field as valuable as a phone number; as such, my assumption is Twitter has had a field in their database for a user’s phone number since it was first released.

Twitter’s been collecting phone numbers since at least late 2006:

https://web.archive.org/web/20061103054924/http://twitter.co...

So what you are saying is that when they started they required phone numbers? As in, what the commenter I was replying to wrote was not true? The 'footnote' in history seems pretty important when the whole point is that ignoring it leads you to assume things that are wrong.

I’ve done something similar and my guess is they preformed a migration in 2009 and didn’t want to force current users to provide phone numbers so they used the default value as a placeholder/note that reminds them to special case these users who were grandfathered in under the old rules.