The following are entirely possible:
- There are fewer moderators around on a Sunday night (GMT).
- More of the moderators and users spend more time with their
$DAYJOB on Monday morning.
- More spammers are spamming on Sunday night and Monday morning because they don't have the brains or transferable skills to hold down a job.
I'm not sure if any of those are actually true though.
We know we have a moderation window (after US goes to sleep and India wakes up) which is why there is the following in the election text this year:
Your existing Community Moderators would also positively encourage potential moderators from the China, Singapore, Indonesia & Australia time-zones to cast their name into the ballot. Ask Ubuntu is a 24 x 7 site and we need community moderators with experience throughout the world from all walks of life.
But you have to consider that it's not just about moderators. Users can (and often do) deal with spam without having to involve a moderator, just by flagging it appropriately. If there is more spam present (and again, we're yet to confirm that there is such a phenomenon), perhaps this suggests there are fewer users on the site too.
And given that we're an English site, I wouldn't be surprised if more East Asian users found support elsewhere. This may ultimately just be something we have to accept and deal with.