Ethereum Altair
Where this time comes from
1606824023 + 74,240 × 32 × 12
= 1635332183
— which is 27 October 2021, 10:56 UTC.
No node answered this, and no data vendor sold it. The same arithmetic reproduces
every Ethereum upgrade since Altair to the second, which
bin/check-calendar.php asserts on every run.
Put that beside a proof-of-work halving, where
the same question has a five-week answer: one of these chains knows the second, and
the other cannot know the month.
The first beacon chain upgrade: sync committees, and the penalties that had been left at introductory levels since genesis.
The activation time is derived, not reported: epoch 74,240 x 32 slots x 12 seconds after the beacon chain genesis at 1606824023. No node and no data vendor is involved, and the same arithmetic reproduces every other upgrade on this list to the second.
Where this came from
Checked against those sources by a person on 23 September 2026. A curated calendar’s only claim to trust is that somebody looked.
More on Ethereum, including what we measure it costs to sell.