Leviticus 23 — The Calendar of the Feasts
Leviticus 23:1-44
An entire chapter of Torah is a liturgical calendar. The feasts are called 'the feasts of the LORD' — his appointed times, not Israel's inventions — and each is fixed to a day.
The structure
Sabbath; Passover on the fourteenth of the first month; Unleavened Bread from the fifteenth; Firstfruits; the counting of fifty days to Weeks (Pentecost); Trumpets on the first of the seventh month; the Day of Atonement on the tenth; Tabernacles from the fifteenth for seven days.
The formula
'These are the feasts of the LORD, even holy convocations, which ye shall proclaim in their seasons' (23:4). The possessive is the point: these particular appointed times are presented as God's own, with dates specified, not left to convenience.
The counted feast
Weeks/Pentecost is not given a calendar date at all. It is counted — fifty days from the sheaf offering (23:15-16). A counted feast behaves exactly like a computed Paschal date, which is why the later Christian argument about computing Pascha is not as foreign to the biblical pattern as it first appears.