a day: the unit by which dates are fixed and lengths of time are counted, and in the plural a whole span of days such as a reign or an age
All sixteen appearances of this word sit in the Aramaic sections of Ezra and Daniel, and most of them are ordinary bookkeeping about time. A temple is finished on the third day of a named month. Supplies are to be handed over day by day. A decree bans prayer for thirty days, and Daniel keeps praying three times a day anyway. In places like these the word does exactly what the English word "day" does.
The plural is where it stretches. In Aramaic, as in Hebrew, "days" can stand for a whole period rather than a run of single days, so the phrase for the days of someone's father means the years he reigned, and the phrase for days of old means as far back as the records go. English keeps the same picture, but a reader can miss that such a phrase is naming a span of time rather than counting sunrises.
Two of those plural phrases carry weight far beyond their size:
- The phrase usually rendered "in the latter days" points to the stretch of time when God brings his purposes to their end, and it frames the whole dream Daniel interprets for Nebuchadnezzar.
- The phrase usually rendered "the Ancient of Days" is a title for God himself, picturing him as one whose years reach back behind every throne in the vision.
Aramaic has other words for time, and they divide the ground differently. A stretch of unspecified length is a season or period (עִדָּן); a fixed appointment is a set time (זְמַן); time without limit is perpetuity (עָלַם), which is the very word that completes the phrase for days of old. This word is the countable one, the day you can put a number on.