Since I teach six classes a day in various courses, I don't trust myself to answer that dreaded question 'what did we do yesterday?' exactly correct every time. My solution is to create 'assignment sheets' which are posted on the bulletin board. Each page is dated for the week and contains a chart for all my classes. The days of the week are listed across the chart and the name of the course is listed down the left margin. Each class has a one-inch box for each day of the week. At the end of each class, I write down the page numbers we have covered, and any quizzes or worksheets. If an assignment needs more in-depth explanation, I simply write 'see me.' When students return from an absence, they know to check the assignment sheets, which are more accurate than my long-term memory.