בִּשְׁנַ֨ת שֵׁשׁ־מֵא֤וֹת שָׁנָה֙ לְחַיֵּי־נֹ֔חַ בַּחֹ֙דֶשׁ֙ הַשֵּׁנִ֔י בְּשִׁבְעָֽה־עָשָׂ֥ר י֖וֹם לַחֹ֑דֶשׁ בַּיּ֣וֹם הַזֶּ֗ה נִבְקְעוּ֙ כָּֽל־מַעְיְנֹת֙ תְּה֣וֹם רַבָּ֔ה וַאֲרֻבֹּ֥ת הַשָּׁמַ֖יִם נִפְתָּֽחוּ׃
אין דעם זעקס הונדערטסטן יאָר פֿון נֹחס לעבן, אין צװײטן חודש, אין זיבעצנטן טאָג פֿון חודש, אין דעם דאָזיקן טאָג האָבן אױסגעבראָכן אַלע קװאַלן פֿון גרױסן תּהָום, און די פענצטער פֿון הימל האָבן זיך געעפנט.
Mishnah Eduyot
Also he used to say that there are five things that last twelve months:The judgment of the generation of the flood [continued] twelve months; The judgment of Job [continued] twelve months; The judgment of the Egyptians [continued] twelve months; The judgment of Gog and Magog in the time to come [will continue] twelve months; The judgment of the wicked in gehinom [continues] twelve months, for it is said, and “It will be from one month until its [same] month” (Isaiah 66:23). Rabbi Yohanan ben Nuri says: “[As long as] from Passover to Shavuoth, for it is said, “And from one Sabbath until its [next] Sabbath” (ibid.).