Lev 23:9-14 Is talking about First Fruits. (3 bible translations) This is another Holy Day mentioned in Lev 23.
First fruits (NIV)
9 The LORD said to Moses, 10 "Speak to the Israelites and say to them: 'When you enter the land I am going to give you and you reap its harvest, bring to the priest a sheaf of the first grain you harvest. 11 He is to wave the sheaf before the LORD so it will be accepted on your behalf; the priest is to wave it on the day after the Sabbath. 12 On the day you wave the sheaf, you must sacrifice as a burnt offering to the LORD a lamb a year old without defect, 13 together with its grain offering of two-tenths of an ephah  of fine flour mixed with oil-an offering made to the LORD by fire, a pleasing aroma-and its drink offering of a quarter of a hin  of wine. 14 You must not eat any bread, or roasted or new grain, until the very day you bring this offering to your God. This is to be a lasting ordinance for the generations to come, wherever you live.
The Sacrifices this day are different
from the Sacrifices of Pentecost
Leviticus 23 (NASB)
9 Then the LORD spoke to Moses, saying,
10 "Speak to the sons of Israel and say to them, 'When you enter the land which I am going to give to you and (1) reap its harvest, then you shall bring in the sheaf of the first fruits of your harvest to the priest.
11 'He shall wave the sheaf before the LORD for you to be accepted; on the day after the sabbath the priest shall wave it.
12 'Now on the day when you wave the sheaf, you shall offer a male lamb one year old without defect for a burnt offering to the LORD.
13 'Its (2) grain offering shall then be two-tenths of an ephah of fine flour mixed with oil, an offering by fire to the LORD for a soothing aroma, with its drink offering, a fourth of a  hin of wine.
14 'Until this same day, until you have brought in the offering of your God, (3) you shall eat neither bread nor roasted grain nor new growth. It is to be a perpetual statute throughout your generations in all your dwelling places.
The Feast of First fruits
9 And the LORD spoke to Moses, saying, 10"Speak to the children of Israel, and say to them: "When you come into the land which I give to you, and reap its harvest, then you shall bring a sheaf of the first fruits of your harvest to the priest. 11He shall wave the sheaf before the LORD, to be accepted on your behalf; on the day after the Sabbath the priest shall wave it. 12And you shall offer on that day, when you wave the sheaf, a male lamb of the first year, without blemish, as a burnt offering to the LORD. 13Its grain offering shall be two-tenths of an ephah of fine flour mixed with oil, an offering made by fire to the LORD, for a sweet aroma; and its drink offering shall be of wine, one-fourth of a hin. 14You shall eat neither bread nor parched grain nor fresh grain until the same day that you have brought an offering to your God; it shall be a statute forever throughout your generations in all your dwellings.
These Sacrifices are also different from the one of Unleavened Bread week.
One would conclude: If this feast would be a feast with symbolism for Firstfruits, then It would also be a symbol of Christ who is the First fruit or Firstborn. The Jews have never admitted that Christ came as a "Savior (Firstborn) first fruit". Apparently this Holy Day mentioned here has been omitted from many churches because on some years it may coincide with a Pagan Holiday. Apparently the Jews had to omit it in their (as some have taught) oracles because it would picture Christ and the meaning. It also calls it an ordinance forever, in the same manner as the other holydays in this same chapter.
When does a day start?