No federal law prevents your employer from making changes to your regular work schedule or from requiring you to work overtime. Nevertheless, your employer may have to raise your hourly rate of pay for any additional hours that you work. Aside from federal laws, employers must also abide by state laws and in some instances state laws limit the ability of your employer to change your regularly scheduled hours.
Under the federal Fair Labor Standards Act your employer must pay you an hourly rate equal to 150 percent of your standard wage for hours worked in excess of 40 hours during a specific week. Your employer can make you work nights or weekends without having to raise your hourly rate as long as you do not work for more than 40 hours per week. However, certain employees, including managers and administrative staff who earn in excess of $23,600 per year, are exempt from the provisions of the FLSA. If you are an exempt employee then federal laws neither limit your working hours nor impacts your rate of pay.
Many states have employment laws that specifically address the issue of employers requiring employees to work overtime. However, these laws typically benefit your employer rather than you. In Montana, for example, your employer can make you work for as long as necessary although working hours are limited for people in certain types of professions. In Minnesota, not only can your employer require you to work overtime without prior notice, but your employer also has the right to terminate you for failing to work the assigned hours.
Aside from being able to make you work overtime, employers in states such as Minnesota and Oklahoma can change your regular working schedule at any time without prior notice. However, in Washington state your employer must provide you with at least two days notice of a temporary change in your working hours. Employees do not have to provide you with advance notice during emergency situations as defined by your employer. In the same state, your employer must provide you with notice of at least seven calendar days for a permanent change in your work schedule.
If you work additional hours during the early part of the week then your employer can normally reduce your working hours for the remainder of the week so as to avoid having to pay you overtime. However, an employer cannot avoid paying overtime by reducing your work hours during a subsequent week.
If you are part of a union then your working hours may form part of a collective bargaining agreement. In such instances your employer cannot change your schedule or require you to work overtime unless the collective bargaining agreement includes a provision for making such changes.