The regression check is to make beta promotion easier, so it makes more
sense to use the Tuesday of the release week (T-2) as the end point of the
regression prevention, instead of Thursday (T-0). But since the beta
promotion PR is sent at Tuesday evening at UTC, the protection should
include the whole Tuesday as well, meaning the 6-week cycle will start from
Wednesdays.

This will also move the start of the regression protection week one day
earlier.