Albert Barnes Commentary Numbers 9:22

"Whether it were two days, or a month, or a year, that the cloud tarried upon the tabernacle, abiding thereon, the children of Israel remained encamped, and journeyed not; but when it was taken up, they journeyed." — Numbers 9:22 (ASV)

A year - literally, “days,” idiomatically a year (Leviticus 25:29), an expression equivalent to “a full period,” though not necessarily the period of a year.