The reason for this, according to legend, is that during the Thirty Years' War the invading Swedes had promised, when laying siege to Brno, that they would call off their attack if they had not succeeded in taking the city by midday on the 15th of August.
Menurut legenda, alasannya adalah karena pada masa Perang Tiga Puluh Hari, pasukan Swedia berjanji saat sedang mengepung Brno bahwa mereka akan menghentikan serangan mereka jika mereka tidak berhasil merebut kota ini pada tengah hari tanggal 15 Agustus.