IEC 62054-21:2004+A1:2017 specifies particular requirements for the type test of newly manufactured indoor time switches with operation reserve that are used to control electrical loads, multi-tariff registers and maximum demand devices of electricity metering equipment. This publication is of high relevance for Smart Grid. THIS CONSOLIDATED VERSION CONSISTS OF THE FIRST EDITION (2004) AND ITS AMENDMENT 1 (2017). THEREFORE, NO NEED TO ORDER AMENDMENT IN ADDITION TO THIS PUBLICATION. The contents of the corrigendum of March 2018 have been included in this copy.