Leviticus 8:4

And Moses did as the Lord commanded him
He convened Aaron and his sons, and the heads of the people, at the door of the tabernacle, and came himself, and brought with him the garments, the oil, and sacrifices, even everything necessary for the consecration: and the assembly was gathered together unto the door of the
tabernacle of the congregation;
and this was, according to the Targum of Jonathan, on the twenty third day of the month Adar or February; but it rather seems to be later, some time in the beginning of Nisan or March, and before the passover began, see ( Numbers 9:1-5 ) .