Every once in a while, the Tech Support team at the office I work in will send out an announcement.
"Server Such-and-So, providing these CompanyProcess sites, will be laid-down-for-a-nap/moved-to-a-new-host/unavailable during the hours of 10:00 PM to 02:00 AM this Sunday."
That kind of work cannot be done during normal business hours, but still needs to be done. I pity the IT guy who got tasked with those jobs over the weekend.
Then I learned about people who have to do similar things on a radio tower, in the dead of night, because workers can't get too close to the transmitter when it is on at full strength.
That's a hard task. Especially when Murphy's Law overshadows the "quick job" with lots of unpleasant surprises.
I guess every business has tasks that are hard to do, but often relegated to the line-workers at odd hours. Some businesses generate more trouble than others in that category, though.