John Gill Commentary Deuteronomy 16:13

"Thou shalt keep the feast of tabernacles seven days, after that thou hast gathered in from thy threshing-floor and from thy winepress:" — Deuteronomy 16:13 (ASV)

You shall observe the feast of tabernacles seven days
Which began on the fifteenth day of Tisri, or September; see (Leviticus 23:34) , &c.

after that you have gathered in your corn and your 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.