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Until the real hardfork, every time the testnet starts, it bootstraps on HF19. Then it reaches the time when the hardfork is set to activate. So it's happened twice. Once on the 10th and again on the 20th.

Good thing there's an obvious place to know when all these starts and stops happen and we don't have to stop building our own projects and shepherding users in communities and explaining whats going on during outages and such long enough to also watch an off chain location for git commits just in case they randomly happen now and then :D

But still even if we DID notice random things in off chain places, 14 days is not 30. Just saying, from your link above:

Update testnet HF time

testnet-09102018
@mvandeberg
mvandeberg committed 14 days ago

There was also the initial announcement:

https://steemit.com/hardfork20/@steemitdev/hardfork-20-testnet-details

Related github:

https://github.com/steemit/steem/commit/3a0f9448bb1e59af7835e444c80ea094aab627c2

So that one activated HF20 on 2018-08-27 17:00:00 UTC. I remember there being two. I guess there were three. I probably got that mixed up because of the halt.

If even you got mixed up.... ;)