The-Day הַיּ֔וֹם “Ha-Yom” is distinct in Job אִיּוֹב “Iyov” 2:1 when הַשָּׂטָן Ha-Satan came before יְהֹוָֽה YHVH in Heaven:
Now [The-Day] came about that the divine beings presented themselves before YHVH. [Ha-Satan] came along with them to present himself before YHVH ( וַיְהִ֣י הַיּ֔וֹם וַיָּבֹ֙אוּ֙ בְּנֵ֣י הָֽאֱלֹהִ֔ים לְהִתְיַצֵּ֖ב עַל־יְהֹוָ֑ה וַיָּבֹ֚א גַם־הַשָּׂטָן֙ בְּתֹכָ֔ם לְהִתְיַצֵּ֖ב עַל־יְהֹוָֽה )
Similar to a distinct י֔וֹם “Yom” (experienced during creation) in Genesis בְּרֵאשִׁ֖ית “Bereshit” 1:3 when לָיְלָה night comes before the presence of light.
“And Elohim called the light - Day, and the darkness He called - Night, and it was evening and it was morning, one day.” ( וַיִּקְרָ֨א אֱלֹהִ֤ים לָאוֹר֙ י֔וֹם וְלַח֖שֶׁךְ קָ֣רָא לָ֑יְלָה וַֽיְהִי־עֶ֥רֶב וַֽיְהִי־בֹ֖קֶר י֥וֹם אֶחָֽד )
If we understand “The-Day” in Job 2:1 in context of Revelation 21:22-25, then The-Day in Heaven never ends since there is no night in the presence of YHVH.
[Revelation 21:22-25, NASB]
“I saw no temple in it, for the Lord God the Almighty and the Lamb are its temple. And the city has no need of the sun or of the moon to shine on it, for the glory of God has illuminated it, and its lamp is the Lamb. The nations will walk by its light, and the kings of the earth will bring their glory into it. In the daytime (for there will be no night there) its gates will never be closed;
Based on Revelation 21 & Job 2, the presence of Ha-Satan before HaShem interrupts The (unending) Day to dinstinguish a moment in Elohim’s timeline when angels noticed night entered Heaven.