Charles Ellicott Commentary 2 Chronicles 3:2

"And he began to build in the second [day] of the second month, in the fourth year of his reign." — 2 Chronicles 3:2 (ASV)

In the second day of the second month. —Hebrew: in the second month in the second. The versions omit the repetition, which is probably a scribe’s error. “On the second day” would be expressed in Hebrew differently. Read simply: And he began to build in the second month, i.e., in Zif (or April—May). See 1 Kings 6:1.