When Gad, Reuben and the half tribe of Manassah settled in the land, though the fighting men continued on with the rest of the tribes per Moses' instruction, the families themselves, having come into their allotment of the promised land that spring before everyone else, had the Feasts of the Lord to keep that first year.

In the time of Christ I understand that people were bringing the firstfruit of the wheat, planted in the winter, to the Lord at the end of the initial count of seven weeks, and folks also brought other firstfruits harvests along with the new wine to the Lord after another 50 day count.  God wanted their first fruit offerings and so the people were living in obedience.

However, the tradition of bringing the firstfruits of the winter-planted wheat at the end of the initial count of seven weeks did not make that point in time the Feast of Harvest Moed.  I believe the only Feast of Harvest Moed would only be about the 1st of the 5th, or 50 days later.  

The Feast of the Harvest was a big party . . . with wine.

A reason for my thinking on timing is found in the following, using Young's Translation of the scriptures:

 14‘Three times thou dost keep a feast to Me in a year; 15the Feast of Unleavened things thou dost keep; seven days thou dost eat unleavened things, as I have commanded thee, at the time appointed [in] the month of Abib; for in it thou hast come forth out of Egypt, and ye do not appear [in] My presence empty; 16and the Feast of Harvest, the first fruits of thy works which thou sowest in the field; and the Feast of the In-Gathering, in the outgoing of the year, in thy gathering thy works out of the field. 17‘Three times in a year do all thy males appear before the face of the Lord Jehovah.

Notice the instruction for the middle one, the Feast of Harvest.  The children of Israel were to present first fruits of that which "they sowed in the field".  So, that very first year the only wheat they could use for the two loaves wave offering would be from wheat they had planted that spring.  That spring-planted wheat needed about four months to grow.

In other words, though the count of seven weeks is essential in determining the timing of the Feast of Harvest, that initial 7 week mark in time is not a Moed.  Another 50 days is required.  

There is confusion that can be generated amongst watchers when a distinction is made in calling the end of the seven week count Shavuot and the end of another 50 day Pentecost.  It is not wrong, but in the scriptures God does not require four Moed to Jerusalem, only three.

My point is that this weekend of June 15-16, though it is the end of the count of 7 weeks, it is not the Moed.

Also, when God came down at Mount Sinai on the 17th/18th day of the 3rd month, that day this year is in another week.

What is being called Shavuot nowadays is not when God came down on Sinai.  I believe that common idea in Judaism is not accurate.

For what it is worth.