New Living Translation
They assisted with the burnt offerings that were presented to the LORD on Sabbath days, at new moon celebrations, and at all the appointed festivals. The required number of Levites served in the LORD’s presence at all times, following all the procedures they had been given.

American Standard Version
and to offer all burnt-offerings unto Jehovah, on the sabbaths, on the new moons, and on the set feasts, in number according to the ordinance concerning them, continually before Jehovah;

Berean Study Bible
Whenever burnt offerings were presented to the LORD on the Sabbaths, New Moons, and appointed feasts, they were to serve regularly before the LORD in the numbers prescribed for them.

Douay-Rheims Bible
As well in the oblation of the holocausts of the Lord, as in the sabbaths and in the new moons, and the rest of the solemnities, according to the number and ceremonies prescribed for every thing, continually before the Lord.

English Revised Version
and to offer all burnt offerings unto the LORD, in the sabbaths, in the new moons, and on the set feast, in number according to the ordinance concerning them, continually before the LORD:

King James Bible
And to offer all burnt sacrifices unto the LORD in the sabbaths, in the new moons, and on the set feasts, by number, according to the order commanded unto them, continually before the LORD:

World English Bible
and to offer all burnt offerings to Yahweh, on the Sabbaths, on the new moons, and on the set feasts, in number according to the ordinance concerning them, continually before Yahweh;

Young's Literal Translation
and for all the burnt-offerings -- burnt-offerings to Jehovah for sabbaths, for new moons, and for appointed seasons, by number, according to the ordinance upon them continually, before Jehovah.

1 Chronicles 23:31 Additional Translations ...