Unless there is an employment contract, union agreement or company policy providing otherwise, an employer can implement a furlough day at any time with or without notice. Additionally, since vacation days are provided at the discretion of an employer (that is they are not legally obligated to give them at all), an employer has a great deal of say if and when such time may be taken.The fact is that in an "at will' business relationship, an employer has a great of latitude in setting the terms and conditions of the workplace. An employee for their part, can either comply or quit, their choice.Note: Additionally, if an employee (or class of employees) is singled out for differing treatment and actionable discrimination is the reason, then the employee(s) would have a claim.