The phrase, each on its proper day
is a formula, which means to do what is right and proper on the day that it has been assigned (see Exodus 5:13, Exodus 5:19). The phrase is often used in administrative contexts (see 2 Kings 25:30; Nehemiah 11:23).
37 “These are the appointed feasts of the LORD, which you shall proclaim as times of holy convocation, for presenting to the LORD food offerings, burnt offerings and grain offerings, sacrifices and drink offerings, each on its proper day,