Lev 23: Subject of First Fruits:
9 And the Lord spake unto Moses, saying,
10 Speak unto the children of Israel, and say unto them, When ye be come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring a sheaf of the firstfruits of your harvest unto the priest:
11 And he shall wave the sheaf before the Lord, to be accepted for you: on the morrow after the sabbath the priest shall wave it.
If we are looking at prophecy to be fulfilled this weekend (May 19-20) then the firstfruits would be waived on the morrow after Shabbat. Saturday at Sundown to the same on Sunday. Sunday is the day we have been on alert about, and then 7 days later Shavuot. So it seems to me firstfruits would be the starting on eve on 19th-eve of 20th.