Leviticus 23 lists every festival on the Jewish calendar. The Targum Jonathan transforms it from a schedule into an instruction manual, adding measurements, procedures, and theological explanations the Hebrew Bible never provides.
Passover falls "in the month of Nisan, on the fourteenth day of the month, between the suns"—the Targum's term for twilight. The sheaf of first fruits is waved "after the first festal day of Pascha," and the Targum counts forward: seven complete weeks, then fifty days, culminating in Shavuot, the feast of weeks.
Rosh Hashanah (the Jewish New Year) is placed "in Tishri, which is the seventh month"—the Targum names the month, which the Hebrew Bible does not. It is called "a memorial of trumpets," a festival of seven days.
The five afflictions of Yom Kippur (the Day of Atonement) get their fullest enumeration here: "from food, and from drink, and from the use of the bath, and from anointing, and the use of the bed, and from sandals." The Hebrew says only "afflict your souls." The Targum lists six specific deprivations, creating the halakhic framework that would become normative practice.
But the most remarkable additions come with Sukkot (the Festival of Tabernacles). The Targum provides exact construction specifications for the sukkah: "two sides according to their rule, and the third a handbreadth higher, that its shaded part may be greater than that into which cometh the sunshine." The dimensions: "in measure seven palms, but the height within ten palms." It must be built "from different kinds of materials which spring from the earth and are uprooted." These measurements are absent from the Hebrew and anticipate later Talmudic discussions.
The reason for dwelling in booths gets a mystical reading: "that your generations may know how, under the shadow of the cloud of glory, I made the sons of Israel to dwell." The sukkah is not a tent. It is a replica of God's protective cloud.