When Is Saturday? is a 1981 Sesame Street storybook featuring Grover. Grover's uncle George is coming for a visit on Saturday, and Grover is very excited. However, it is only Sunday, and Grover can't keep track of all the days between then and his uncle's arrival. After his mother makes him a calendar, the story follows Grover through his week, noting each day and showing all the things he does to keep himself occupied in the days leading up to his uncle's visit.