Deuteronomy 16:13

Thou shalt observe the feast of tabernacles seven days,.... Which began on the fifteenth day of Tisri, or September; see Leviticus 23:34, c.

after that thou hast gathered in thy corn and thy wine and therefore sometimes called the feast of ingathering, Exodus 23:16, barley harvest began at the passover, and wheat harvest at Pentecost; and before the feast of tabernacles began, the vintage and the gathering of the olives were over, as well as all other summer fruits were got in.