Isaiah 13:22 (King James Bible) and her time is near to come and her days shall not be prolonged
Here the King James Bible has the plural days, while the Book of Mormon text has the singular day. The singular her day is consistent with her time in the previous line. Of course, the Book of Mormon reading could involve an error in the early transmission of the text (the original manuscript is not extant for this part of verse 22). The Hebrew original for Isaiah 13:22 has two indicators of plurality: the word for her days and the plural ending of the associated verb. So it seems less likely that the singular day is due to an error in the Hebrew.
If day is an error for days in 2 Nephi 23:22, it could have occurred as Oliver Cowdery, the scribe here in 𝓞, took down Joseph Smith’s dictation. As David Calabro points out (personal communication), it would have been difficult here for Oliver to have heard the difference between day shall and days shall since both z and ¸s are sibilants. In other words, Oliver could have readily misinterpreted /deiz ¸sæl/ as /dei ¸sæl/, especially since he might have expected the singular her day, given the preceding occurrence of the singular her time. For a similar example of the possibility of mishearing a sequence of sibilants, see the discussion under verse 18 of “eye(s) shall”.
Another possibility is that such an error could have occurred as Oliver Cowdery copied the text from 𝓞 into 𝓟. We have considerable evidence that in the manuscripts Oliver sometimes omitted the plural s for days:
Thus the singular day in 2 Nephi 23:22 could be an early transmission error for days. (For two more examples that may involve an error of day for days, see Alma 50:23 and Helaman 8:16.)
Despite this manuscript evidence, the singular day will work in 2 Nephi 23:22. Thus the critical text will maintain the singular day, even though this reading could very well be due to an early transmission error.
Summary: Retain in 2 Nephi 23:22 the singular day, the reading of the earliest textual source (the printer’s manuscript); the singular her day parallels the use of her time in the previous clause.