Can an employer force you to work on your day off?

Yes, your employer can require you to work on your day off. There are no specific laws that state you need to have significant notice before working an additional shift, so there is nothing illegal about an employer having you come into work for more shifts that were not previously mentioned.

Now, you do have the option to either accept the additional work or deny it. If you do deny it, it is important to note that in most cases, it would be entirely legal for an employer to fire someone over refusal to come work overtime. This employer right is protected under the Fair Labor Standards Act.