How long did Jehoiachin rule over Jerusalem?

2 Kings 24:8 and 2 Chronicles 36:9

1. Three months (2 Kings 24:8) - "Jehoiachin was eighteen years old when he became king, and he reigned three months in Jerusalem; and his mother’s name was Nehushta the daughter of Elnathan of Jerusalem," (NASB).
2. Three months and ten days (2 Chronicles 36:9) - "Jehoiachin was eight years old when he became king, and he reigned three months and ten days in Jerusalem, and he did evil in the sight of the Lord," (NASB).

The discrepancy in duration is due to a copyist error.  We can see that the difference time is 10 days.  The system of number notation used by the Jews at the time of Ezra consisted of horizontal hooks that represented decades, or "tens."  would equal the number 14 where would be 24.  If one or both of the hooks were smudged or flaked off of a papyri, then the dates would be off by a value of ten.  Therefore, most probably, the correct value was three months and ten days since the hook could easily have flaked off in a copy.

Does this mean the Bible is not trustworthy?  Not at all.  Inspiration is ascribed to the original writings and not to the copies.  Scribes made errors.  However, the errors were very infrequent and from other information in the Bible, we can easily ascertain what the correct age is.