This question has been asked and answered in the German media in 2020 iirc - the institute doing the counting, the Robert Koch Institute, has an explanation in

This question has been asked and answered in the German media in 2020 iirc - the institute doing the counting, the Robert Koch Institute, has an explanation in their FAQ [0], to paraphrase: In general, there are fewer cases reported to the RKI on weekends, since a) fewer people go to a doctor on the weekends (since normal pcp's offices are closed in Germany) - this leads to fewer samples being tested and thus, fewer cases reported and b) additionally not all of the local communities have active health departments on the weekends, so this contributes to a drop of reported cases on the weekend. [0] https://www.rki.de/SharedDocs/FAQ/NCOV2019/FAQ_Liste_Fallzahlen_Meldungen.html https://www.rki.de/SharedDocs/FAQ/NCOV2019/FAQ_Liste_Fallzah...