since they had been unable to observe it at the regular time, because not enough priests had consecrated themselves and the people had not been gathered in Jerusalem.

2 Chronicles 29:17
They began the consecration on the first day of the first month, and on the eighth day of the month they reached the portico of the LORD. For eight more days they consecrated the house of the LORD itself, finishing on the sixteenth day of the first month.

2 Chronicles 29:34
However, since there were not enough priests to skin all the burnt offerings, their Levite brothers helped them until the work was finished and until the priests had been consecrated. For the Levites had been more diligent in consecrating themselves than the priests had been.

2 Chronicles 30:4
This proposal pleased the king and the whole assembly.

2 Chronicles 30:15
And on the fourteenth day of the second month they slaughtered the Passover lamb. The priests and Levites were ashamed, and they consecrated themselves and brought burnt offerings to the house of the LORD.

2 Chronicles 30:24
For Hezekiah king of Judah contributed a thousand bulls and seven thousand sheep for the assembly, and the officials contributed a thousand bulls and ten thousand sheep for the assembly, and a great number of priests consecrated themselves.

For they could not keep it at that time, because the priests had not sanctified themselves sufficiently, neither had the people gathered themselves together to Jerusalem.