The sentence of the generation of the Flood lasted twelve months, the sentence of the Egyptians lasted twelve months, the sentence of Job lasted twelve months, the sentence of Gog of Magog lasts twelve months, the sentence of the wicked in Gehenna lasts twelve months. Nebuchadnezzar was three and a half years. Sennacherib was over three and a half years. Vespasian was three and a half years.

-Eikhah Rabbah 1:40