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+Date: Thu, 25 Mar 2021 17:02:04 +1000

+From: Anthony Towns <aj@erisian.com.au>

+To: Jeremy <jlrubin@mit.edu>,

+ Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>

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+Subject: Re: [bitcoin-dev] March 23rd 2021 Taproot Activation Meeting Notes

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+

+On Tue, Mar 23, 2021 at 08:46:54PM -0700, Jeremy via bitcoin-dev wrote:

+> 3. Parameter Selection

+> - There is broad agreement that we should target something like a May 1st

+> release, with 1 week from rc1�starttime/startheight,

+> and 3 months + delta stoptime/stopheight (6 retargetting periods), and an

+> �activation time of around Nov 15th.

+

+I'd thought the idea was to release mid-late April, targetting a starttime

+of May 1st.

+

+> - If we select heights, it looks like the first signalling period would be

+> 683424, the stop height�would be 695520.

+

+> - If we select times, we should target a mid-period MTP. We can shift this

+> closer to release, but currently it looks like a 1300 UTC May 7th start time and stop time would be 1300 UTC August 13th.

+

+We've traditionally done starttime/timeout at midnight UTC, seems weird

+to change. Oh, or is it a Friday-the-13th, lets have 13s everywhere

+thing?

+

+Anyway, block 695520 is about 19440 blocks away, which we'd expect to be

+135 days, but over the past two years, 19440 blocks prior to a retarget

+boundary has been between 127 (-8) days and 137 (+2) days, and in the

+last four years, it's been between 121 (-14) days and 139 (+4) days. [0]

+

+So given block 676080 had mediantime 1616578564, I think picking a

+mediantime no later than ~139 days later, ie 1628640000 (00:00 UTC

+11 Aug) would be the most likely to result in MTP logic matching the

+height parameters above, and a day or two earlier still might be better.

+(It will match provided MTP passes the timeout at any block in the range

+[695520, 697535])

+

+> (please check my math, if anyone is superstitious we can add a day to times...)

+

+It looks to me like blocks are more likely to arrive earlier than later

+(which is what we'd expect with increasing hashrate), fwiw, so adding

+days would be more likely to cause MTP to have more signalling periods

+than height-based, rather than avoid having fewer.

+

+Cheers,

+aj

+

+[0] $ for b in `seq 201600 2016 676000`; do a=$(($b-19440)); echo $(( $(bitcoin-cli getblockheader $(bitcoin-cli getblockhash $b) | grep mediantime | cut -d\ -f4 | tr -d ,) - $(bitcoin-cli getblockheader $(bitcoin-cli getblockhash $a) | grep mediantime | cut -d\ -f4 | tr -d ,) )); done

+