I have personally delivered packages at the main UPS sorting center here on a Saturday evening to make sure they were shipped out on a Monday, not sure if I'd be welcome on a Sunday (probably a union thing) but surely in China anything is possible. If I look at the dates of the tracking you see loads of activity on a Sunday.
The only country I've dealt with so far that had a different workweek was in the Middle East. Iran has a Thursday/Friday weekend due to religious traditions. Israel has a work week that starts on a Sunday.
And I'm not sure why my 'cal' command always generates this:
Su Mo Tu We Th Fr Sa
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31
For some people the workweek does start on a Sunday.
Our lab is open 24/7, no weekend here ;-)