an indexing unit in the form of a disc or an endless tape for switching chronometers has a number of programmable switch tabs disposed at an edge of the element forming a unitary structure , the switch tabs being depressable against the influence of a restoring force for positioning selected tabs in at least one programming position for actuating a separate switch device for switching a chronometer . the indexing element is comprised of flexible foil having a number of uniformly spaced incisions at an edge thereof . each tab formed between successive incisions has a free end which may be pressed behind a retaining element for programming the indexing element .