I know most of us are in the US, but this is an international website. He could be anywhere in the world.

a military base.

I doubt someone was sitting around watching all day and noting the changes manually. Probably enough people here that could make some small monitoring bot (or know enough to ask one of the AIs to write the code for them) to monitor and log.  

 
I think this site is based on UTC (GMT for the older naming) so US time not all that relevant.

 
But maybe it's a big purge of reviews or something like a DB crash and recovery and that is how many were submitted between the time data could be recovered/restored and when the problem occurred. I guess it might be interesting to some but for me meh, the world is a dynamic place with lots of random things occurring.

I think it was sometime around 10 years ago reviews hit the 1 million mark -- IIRC there was even a poll/competition to see who could guess when that would happen. Forget how much VIP was given to the winner but want to say something like a year.