What is "ossensamstag"

Ossensamstag (derived from Ossenbrügge, Low German for Osnabrück) is the name used in Osnabrück, Germany to refer to the Saturday before Rosenmontag, on which carnival processions through the city have taken place since 1976. Every year the processions attract tens of thousands of spectators, watching the carnival floats pass along the route leading from the Johanniskirche via Neumarkt to the Rathaus. The traditional cry of “Osna Helau!” is derived from the city's name. Until 2014 NDR broadcast the procession live on television; since 2015 it has been available as a livestream broadcast.