The ornamental design for a "teaching aid for learning to tell time," substantially as shown and described.
FIG. 1 is a front elevational view of a teaching aid for learning to tell time showing our new design;
FIG. 2 is a front elevational view of FIG. 1, the clock face depicted by means of broken lines being shown for illustrative purposes only and forming no part of the claimed design; and,
FIG. 3 is a left side elevational view thereof, the top, bottom, and right side views being identical thereto.