The ornamental design for a timer, as shown and described.
FIG. 1 is a perspective view of a timer in accordance with the present design;
FIG. 2 is a right side elevational view thereof,
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dot-dash lines shown in the drawings define the bounds of the claimed design, and form no part thereof. The broken lines shown in the drawings illustrate portions of the time that form no part of the claimed design.