Consiglio: Use the word “appointment” when talking to co-workers about your time off.

If you want or need the day off, and you work somewhere where people give you guff about taking time off, just say you have “an appointment” and refuse to elaborate. “Appointment” is generic, professional and applicable to every situation. If asked to elaborate, simply repeat “I have an appointment”. It's none of their business if your appointment is for a doctor, a financial advisor, or a tee time/massage.