Computer lab calendar

I am trying to create an easy to use calendar for teachers to use to schedule the computer lab. We have an 8 period day and I need a way for teachers to only sign up for the periods that they want not the entire day. Right now we are using a google spreadsheet but this means that you have to log in to view who is coming in. I would rather just have a one click method for the lab coaches to view this calendar and still have it break down into periods.