Another interpretation. When he would see the orb of the sun coming and bowing down before the Omnipresent, he knew that it was night, and when he would see the moon and the stars and the constellations coming and prostrating themselves, he knew that it was day. When prayer came before the recitation of the Shema, he knew that it was night. The angel who is appointed over prayer waits until the last congregation in Israel has prayed, and he makes of all the prayers a crown, and he sets it upon the head of the Holy One, blessed be He, as it is said (Proverbs 10:6), "Blessings are upon the head of the righteous one" [read as] upon the head of the Righteous One of the world.
The Angel Who Weaves Israel's Prayers Into a Crown
Yalkut Shimoni on Torah 406:4
דָּבָר אַחֵר. כְּשֶׁהָיָה רוֹאֶה גַּלְגַּל חַמָּה בָּא וְכוֹרֵעַ לִפְנֵי הַמָּקוֹם, הָיָה יוֹדֵעַ שֶׁהוּא לָיְלָה, וּכְשֶׁהָיָה רוֹאֶה הַלְּבָנָה וְכוֹכָבִים וּמַזָּלוֹת בָּאִים וּמִשְׁתַּחֲוִים, הָיָה יוֹדֵעַ שֶׁהוּא יוֹם. כְּשֶׁהָיָה תְפִלָּה קוֹדֶמֶת לִקְרִיאַת שְׁמַע, הָיָה יוֹדֵעַ שֶׁהוּא לָיְלָה. מַלְאָךְ שֶׁהוּא מְמֻנֶּה עַל הַתְּפִלָּה מַמְתִּין עַד שֶׁיִּתְפַּלֵּל כְּנֵסִיָּה הָאַחֲרוֹנָה שֶׁבְּיִשְׂרָאֵל, וְהוּא עוֹשֶׂה כָּל הַתְּפִלּוֹת עֲטָרָה, וְהוּא נוֹתְנוֹ בְּרֹאֹשׁוֹ שֶׁל הַקָּדוֹשׁ בָּרוּךְ הוּא, שֶׁנֶּאֱמַר(משלי י, י) "בְּרָכוֹת לְרֹאשׁ צַדִּיק", לְרֹאשׁ צַדִּיקוֹ שֶׁל עוֹלָם.