When the year was expired - literally, as in the margin, i. e. at the return of the season for military expeditions. The expedition against Jehoiakim took place probably late in the autumn of one year, that against Jehoiachin early in the spring of the next.
Strictly speaking, Zedekiah was uncle to Jehoiachin, being the youngest of the sons of Josiah (marginal note and reference). He was nearly of the same age with Jehoiachin, and is called here his “brother” (compare Genesis 14:14).