We work a manditory 12 hr. shift.

Ok here is our question
our work week starts Sunday-Saturday

We work a rotating shift. So I work Sunday I have Mon. Tues off I then work Wed. Thurs and have Fri. Sat. Sun off the next week I work Mon. Tues and so on.

Now say I had Sunday off. I work Monday and tues. I can be forced to work Wed. and Thursday. Then my next scheduled days to work are Fri. Sat. and Sun. since sunday starts the new week I can be forced to work monday and Tues then work Wed. , Thurs, and I can be forced to work 1 more day which is usually Fri. So we end up working 12 days in a row 12 hrs a day.

Can they do this?

Yes it is legal because beginning on Sunday a new work/calendar week starts. IL One Day Rest in Seven Act does allow for one day rest in a calendar week which IL defines as starting 12:01 Sunday morning and ending at midnight on the following Saturday.

So your first week you are off Sunday and then work the next six days which is ok.

The second calendar week you are working Sunday to Thursday which is ok as well. You are correct in your statement that they can only make you work one more day in this second week whether it be Friday or Saturday. If your employer chooses to make you work Friday and give you off Saturday they can do so.

So you do have one day off in each calendar week which is in accordance with IL One Day Rest in Seven Act.