I’ve worked where being on call for a day was equal to one hour for every eight on call. But try that on a day off, and you lose out on activities because you can’t go to the amusement park or go anywhere but a fifteen minute run to the store.
You’re able to stay at home, but even that has limits.
When you figure that for your on-call stretch, you're on the company's clock 24X7 with no pay, it starts making your compensation look pretty McPoor. Instead of a standard 2000-hour year, if you work one week on-call every month, that's 2 24-hour days of unpaid labor plus 5 16-hour days, for a total of 1536 hours every year you work for nothing. Now divide your salary by 2000 (your standard work year) + 1536 (your giveaway time) and see how much you're making per hour.
Why that is not illegal is beyond me.