John Wesley on 2 Chronicles 30:2

Second month - Which was against the common rule, but the doing of this in its proper time, namely, the fourteenth day of the first month was impossible, because the temple was not cleansed, nor they prepared. As there was a proviso in the law, that particular persons who were unclean in the first month, might keep the passover the fourteenth day of the second month, he doubted not but that might be extended by the whole congregation.