Old Testament readings use the Septuagint , the Scripture the apostles quoted. Masoretic numbering shown for reference.Learn why
LXX

2 Chronicles 29:17

And [Ezekias] began on the first day, [even] on the new moon of the first month, to purify, and on the eighth day of the month they entered into the temple of the Lord: and they purified the house of the Lord in eight days; and on the thirteenth day of the first month they finished [the work].

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