וַיְהִ֣י בַשָּׁנָ֣ה הַ֠חֲמִשִׁית לִיהוֹיָקִ֨ים בֶּן־יֹאשִׁיָּ֤הוּ מֶֽלֶךְ־יְהוּדָה֙ בַּחֹ֣דֶשׁ הַתְּשִׁעִ֔י קָרְא֨וּ צ֜וֹם לִפְנֵ֧י יְהוָ֛ה כָּל־הָעָ֖ם בִּירֽוּשָׁלִָ֑ם וְכָל־הָעָ֗ם הַבָּאִ֛ים מֵעָרֵ֥י יְהוּדָ֖ה בִּירוּשָׁלִָֽם׃
유다 왕 요시야의 아들 여호야김의 오년 구월에 예루살렘 모든 백성과 유다 성읍들에서 예루살렘에 이른 모든 백성이 여호와 앞에서 금식을 선포한지라
Rashbam
'כי קרא שמיטה לה, in other words: the time has come which we know as sh’mittah from Leviticus 23,2. Proclaiming this period as such is similar to proclaiming all the festivals in advance, hence the expression קרא, as in מקראי קודש. Even fast days are proclaimed in advance as we know from Lamentations 1,15, or Jeremiah 36,9.