Avi K: While you are correct it a the yom hadin, there is still an aspect of yom tov to it as stated in Nechemiah 8:10-12 –
10 – יוַיֹּ֣אמֶר לָהֶ֡ם לְכוּ֩ אִכְל֨וּ מַשְׁמַנִּ֜ים וּשְׁת֣וּ מַמְתַּקִּ֗ים וְשִׁלְח֚וּ מָנוֹת֙ לְאֵ֣ין נָכ֣וֹן ל֔וֹ כִּֽי־קָד֥וֹשׁ הַיּ֖וֹם לַֽאֲדֹנֵ֑ינוּ וְאַל־תֵּ֣עָצֵ֔בוּ כִּֽי־חֶדְוַ֥ת יְהֹוָ֖ה הִ֥יא מָֽעֻזְּכֶֽם:
11: יאוְהַֽלְוִיִּ֞ם מַחְשִׁ֚ים לְכָל־הָעָם֙ לֵאמֹ֣ר הַ֔סּוּ כִּֽי־הַיּ֖וֹם קָדֹ֑שׁ וְאַל־תֵּֽעָצֵֽבוּ:
12: יבוַיֵּֽלְכ֨וּ כָל־הָעָ֜ם לֶֽאֱכֹ֚ל וְלִשְׁתּוֹת֙ וּלְשַׁלַּ֣ח מָנ֔וֹת וְלַֽעֲשׂ֖וֹת שִׂמְחָ֣ה גְדוֹלָ֑ה כִּ֚י הֵבִ֙ינוּ֙ בַּדְּבָרִ֔ים אֲשֶׁ֥ר הוֹדִ֖יעוּ לָהֶֽם:
10: And he said to them, “Go, eat fat foods and drink sweet drinks and send portions to whoever has nothing prepared, for the day is holy to our Lord, and do not be sad, for the joy of the Lord is your strength.”
11: And the Levites quieted all the people, saying, “Hush, for the day is holy, and do not be sad.”
12: Then all the people went to eat and to drink and to send portions and to rejoice greatly, for they understood the words that they informed them of.