The nationwide warning day is a joint initiative of the federal, state and local governments and is held every year on the second Thursday in September. In 2024, this day falls on 12th September. From 11:00 a.m., a test warning is sent via the federal government’s Modular Warning System (MoWaS) to various warning multipliers, such as radio stations and apps, which then forward this message to warning devices such as televisions, radios and smartphones. At the same time, local warning devices such as sirens or loudspeaker vans can also be activated. An all-clear is issued via the same channels at 11.45 am. At present, the all-clear is not yet sent via cell broadcast. The aim of the warning day is to check the technical infrastructure and inform the population about warning processes.
Further information can be found here.