In the United States, employers are legally required to accommodate employees' religious beliefs and practices, unless doing so would impose an undue hardship. In particular, if it does not impose an undue hardship, and employer must make a reasonable attempt to adjust an employee's schedule around a religious holiday. I am wondering whether this applies if the employee is observing the religious holiday for cultural, rather than religious, reasons.
For example, suppose an employee was raised Hindu, and spends Hindu holidays with her family. However, this employee does not truly believe in the religious teachings of Hunduism, but rather observes the holidays because it is part of her culture and tradition is important to her.
Are there examples of court rulings that address this issue?