Unless your employer has changed your work days and hours for an unlawful purpose, generally the answer is yes.  There is also typically standard language in your employee handbook or other policies that states an employer’s right to change days and hours of employment. In addition, California employers are required to give “Notice to Employee” of changes in the employment relationship, although this is rarely done other than initially upon hire.  (See, Labor Code § 2810.5 notice available on www.dir.ca.gov).

Any such notice is usually accompanied with a reminder that nothing in the notice changes the at-will employment relationship.