Unfortunately, there may be nothing you can do about it. That is unless this schedule change violates company policy, a union agreement or employment contract. Also, this change cannot be due to some form of actionable discrimination or retaliation. Otherwise, your employer can make such a change to your working hours with or without notice. The fact is that most employment relationships are what is know as "at will". This means that an employer can set the terms and conditions of the workplace much as it sees fit. An employee for their part, can either agree to them, quit or refuse to comply and risk termination.`