Sometimes people being stingy with the cash works in your favour
I was once heavily involved in a project to convert a whole government building to a fresh network system.
Luckily each small department had its own server, so could be treated as an independent unit.
The aim was for their staff to leave on Friday evening and return to their desks at 09:00 on Monday to find a fresh network stack (LAN Manager!), with all their files and apps intact. This obviously involved weekend working. This was an organisation where a "working day" for us techies meant "until things are working", but weekends would obviously need something extra.
So the firm came up with a scheme - you got £x for each weekend day, plus £y for unsocial hours. You would be expected to take Monday and Tuesday as your "weekend", while a few others did the inevitable mopping up. The company would claw back the £x for each of those days, but you would keep the unsocial hours part.
Then the beancounters obviously leapt in. If you work less than a day, it's pro rata.
That obviously meant that if you worked MORE than 8 hours, it's STILL pro rata.
We would hit one large or two small departments each weekend. So we ended up spending Tuesday to Friday on prep work, creating accounts and groups on LAN Manager and trial running of scripts. On Saturday we would do the bulk of the conversions in 12 hours, On Sunday we would check the data transfers and hit the users' boxes.
Unfortunately that LAN Manager had a stupid "feature" where it only allowed 8 sessions, despite having a licence for many more. Once you reached 8, you needed to reboot the server to get another batch added. Once you reach the new limit, restart it again. This meant touring the offices restarting PCs too - some half a dozen times.
It was usually about 08:00 on Monday when we had got every box up and running at the same time. Big fry-up breakfast in a cafe up the road, then off to bed.
So the overtime was enormous - 4.5 times £x+y, with £x clawed back for our Monday recovery period. For three months, my overtime payment, which had never been seen on my payslip before, was larger than my salary.