The ornamental design for a cross-shaped calendar, as shown and described.
FIG. 1 is a front perspective view of a cross-shaped calendar in accordance with the present invention;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a front thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken line showing of the calendar year, months, days of the week, and day numbers is for the purpose of illustrating alpha-numeric calendar indicia and forms no part of the claimed design.