Assuming that there is no employment contract
or company policy that mandates a fixed schedule, an employer is always free to change an employee's schedule. Certainly it would be ridiculous to think that an employer could change an employee's schedule without the employer having access to that change or otherwise being notified of it, but there is nothing unlawful with changing the schedule the day before someone is scheduled. However, if there was no
way that the employee could have known, then they couldn't be disciplined for missing work. Of course that assumes no ability to know. Otherwise, if they could have checked where the schedule was posted or received a call saying you need to come to work, then they have a duty to show up or can be disciplined for not doing so.
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