Here is a list of dates in July, August and the following months, when important events occur.
BTC1 is the client program created by the results of the New York Agreement, a branch of Bitcoin Core code base. The beta version of BTC1 was released on June 30th. However, according to the proposal of SegWit2x, on July 14 all the miners who signed the New York agreement should install the beta version of BTC1 and test it.
This will not have a big impact on the work of ordinary users or miners.
21 July:
The miners are beginning to signal their readiness to support BIP91 This day the BTC1 nodes will be debugged and ready for operation, but more importantly, this is the day when the miners will start signaling their support for the BIP91.
This also does not affect ordinary users. However, if you are a minor, you can help activate SegWit by giving a signal about your support for BIP91. For this it is necessary to extract blocks signaling bit 4, using BTC1 or another bitcoin client with BIP91 firmware.
July 23 (earliest):
Fixing the results of the BIP91 support In order to activate BIP91, it is necessary that the offer from the 336 last blocks be supported by 269, that is 80%. This will take approximately 2.3 days. Therefore, with the support of the SegWit2x proposal, the fixing of the results can occur, at the earliest, on July 23.
Again, this does not affect ordinary users.
However, if you are a minor and BIP91 will be activated, then you will have a couple more days to join this softphone. Otherwise, you risk that you will get illegitimate blocks.
July 29:
Deadline on BIP91 If the miners do not want a split of the blockade of bitcoin, then July 29 will be their first deadline for them.
In order for BIP91 to be compatible with BIP148 during activation, everything must be fixed on this day no later than 11:00 Moscow time. But the sooner this happens, the better. The closer to the deadline, the higher the risk that activation will not happen on time.
If BIP148 does not have time to activate before this deadline, there may be a split bitcheina bitcoin.
If you are a regular user who is not prepared for a possible split, then you will have two days to prepare.
If you are a minor and BIP91 was not activated on July 29, then you have two days to choose which block to continue mining from August 1: BIP148 or the original Legacy.