Charles Ellicott Commentary 2 Chronicles 30:2

"For the king had taken counsel, and his princes, and all the assembly in Jerusalem, to keep the passover in the second month." — 2 Chronicles 30:2 (ASV)

For the king had taken counsel. — And the king determined (2 Chronicles 25:17). The resolution was taken by the king in council with his grandees and the popular representatives; apparently before the 14th of Nisan, which was the proper time for keeping the feast.

In the second month. —And not in the first month of the sacred year, as the law prescribes (Numbers 9:1–5). The grounds for the postponement are stated in the next verse, namely, the legal impurity of many of the priests, and the non-arrival of the people at the proper time. The law permits postponement to the second month in such cases (Numbers 9:6–11). The first month was Nisan (Assyrian: Nisdnu); the second, Iyyar (Assyrian: ru).