"You cannot receive the stamp at this time."

It seems they disallow you from redeeming the stamp/points when it starts approaching midnight PST. I checked at around 11:52 PM PT, at least by that point.

Interesting! I wonder why they restricted it to certain hours, it certainly isn't listed on the announcement. While we don't have good numbers on the block window, this seems a useful point to add to the page, at least to warn people to not wait until its too late.

Thanks for the information.