now: this present time, and above all the word that turns a letter or a speech to the point it is making
This is the ordinary word for "now" in the Aramaic portions of the Old Testament, and it appears nowhere else: six times in the documents quoted in Ezra, seven times in Daniel. Both settings are official ones, letters carried to and from the Persian court and speeches made in a royal throne room, and that setting shapes what the word is for.
In most of its appearances it is not telling anyone what time it is. It is the word a writer or speaker uses to stop laying out background and get to business. Everything before it is the case being made; everything after it is what the writer actually wants:
- in Ezra 4:21 it introduces the king's order to stop the building work
- in Ezra 5:17 it introduces a request that the royal archives be searched
- in Daniel 3:15 it introduces one last chance to bow before the furnace
- in Daniel 6:8 it introduces the officials' request that the king sign their decree into law
That is why English Bibles so often render it "now therefore" or "now then" rather than a bare "now." The force is closer to "so here is what we are asking" than to "at this moment."
A couple of places do use it for real time. Ezra 5:16 reports that the temple has been under construction "from that time until now," measuring a stretch of years that reaches the present. And when Nebuchadnezzar closes his account in Daniel 4:37 by praising the King of heaven, the word marks where he now stands, on the far side of his madness and his restoration.
The Hebrew word for "now" (עַתָּה) does the same double duty everywhere else in the Old Testament, and the Greek word for "now" (νῦν) does it in the New, so this is a habit of speech shared across all three biblical languages rather than a quirk of Aramaic.