set up an assignment and have it automatically become visible at a time/date

My students will randomly go to assignments or tabs in an assignment and attempt to do the work there. Sometimes they simply go from Tab 1 to Tab 2, which is often not the next logical thing to do, or fail a quiz because they didn't do the work first. I feel like it didn't appear until the time I put on the assingment last year, I could be wrong, but I'd like to be able to assign different parts of the lesson in separate assignments and not have to hide them and then unhide them. If they were able to be scheduled to appear but were not visible before the time I wanted the class to be able to see them it would be so much easier.