How can I restrict a time input value?

I want to display an input type hour from 08:00 to 20:00. I tried this:

<input type="time" id="timeAppointment" name = "timeAppointment" min="08:00" max="20:00" placeholder="hour"  required/>

But when I display it I can still select any time, it does not restrict me as I indicate. What is the problem? If is necessary some code I work with Javascript.