en_tn/neh/08/18.md

day by day

This idiom means "each day." (See: rc://en/ta/man/jit/figs-idiom)

from the first day to the last

The implied information is that it was during the entire week of the festival. Alternate translation: "from the first day to the last day of the week" (See: rc://en/ta/man/jit/figs-explicit)

They kept the festival

"They made a feast" or "They celebrated the festival"

on the eighth day

"on day 8" (See: rc://en/ta/man/jit/translate-ordinal)

solemn assembly

This was a special religious gathering.

in obedience to the decree

The implied information is that "the decree" was the command of Yahweh about how the Festival of Shelters was to end. Alternate translation: "as God had commanded" (See: rc://en/ta/man/jit/figs-explicit)