I suspect that most that used PQ know that. If you create a new PQ there is a "Pocket Query Tips:" on the bottom of the page.
Pocket Queries are generated in Pacific Standard Time (PST). This may mean that your Monday is different from our Monday.
There is a server time clock on the PQ page for that reason
The reason is quite obvious because it makes scheduling of PQ simpler on the server if only one time zone is used. The PQ system and the notification is likely the one oldest part of the website still in use. If I dont miss remember one of the founders that wrote the original code said when he talked on a mega event that those part are the only part that still use the original code.
You could post a suggestion on the groundspeek forum but I would not expect it to change. The more annoying problem with the legacy code is that you cant set any cache type for notification, the change have been requested since I started 6 yeas ago and had not change. Groundspeek tries to move away from PQ and handheld GPS to API and phone apps if you look at their changes. A extention to the GPX format was in the works a few years ago and was delayed an have not been done to this day- Rewriting the scheduling for PQs are likely extremely low on their priority when you can compensate by changing the day to the day before if you need it in the morning.
There was a similar problem with when the date of a log in the apps would get the date of the server and not the date of the user and it took the a long time to fix that and that was a problem.