Spring (10) for clock mechanism, the spring comprising a body (11) extending between a first end (12) of the spring and a second end (13) of the spring, the spring being intended to be connected mechanically to a housing at each of the first and second ends, the spring comprising, between the first and the second end, at least one member (17) intended to act by contact on an element (42) of the clock mechanism, characterized in that the body comprises a deformable zone (14) extending in a curve (18) and in that the curve comprises a first part (18a) that is concave when viewed from the first end.