With Pentecost having a wave offering aspect to the Feast, I believe that an ascension/rapture event is tied to this.

Over the years, my thinking has changed in terms of when Pentecost takes place.  I know that there is a debate between seeing Pentecost taking place on the 50th day after seven full weeks, verses adding a full 50 day count after the completion of a full seven weeks.  Both of these counting options would begin on the Feast of Firstfruits, a few days after Passover.  I am holding to the second option above.  Here is part of the reason why.

It has to do with when Joshua took the Children of Israel over the Jordan and into the Promised Land.  In the first part of Joshua, they cross over in chapter three.  In chapter five, the men get circumcised and shortly thereafter they celebrate the Passover (see 5:10).  After the Passover they eat some of the grain of the land and the giving of manna ceases.  The form of the grain is unleavened, consistent with God's instruction for the Feast of Unleavened Bread.  

Now traditionally, Pentecost would come about 50 days later.  But, here is the thing.  In Exodus 23:16 God had instructed Israel (Moses) that when it comes to this particular harvest feast, that they are to observe it with the first fruits of their labors.  In other words, you have to offer up what you planted.  That was not stipulated for the first fruits offering right after Passover.  That is why it was OK for Joshua and Israel to eat of the land after crossing the Jordan.

Joshua and Israel could not have celebrated that Feast of Pentecost that first year in the promised land, there was not enough time to plant and reap.  However, if the Feast is to be observed actually seven weeks plus another 50 days after the Feast of First Fruits, then it could be done.

This time frame is also consistent with what I observe about the timing of when Moses went up the mountain (18th day, third month).  When he came down with the first set of tablets 40 days later, it would have been on the day of Pentecost according to my count.

Now, when Moses came down with that first set of tablets in hand, finding idolatry in the camp, he asked those who are for the LORD to come to him.  Moses then had those of the tribe of Levi accomplish an initial judgement against the children of Israel and 3000 were killed ( Exodus 32:28).

Fast forwarding to when the Holy Spirit came upon the disciples in the upper room on Pentecost (Acts 2:1), Peter proclaimed a message of repentance and guess how many responded and were added to the assembly?  3000.  To me this is a tie in to when Israel initially lost 3000 in their early years.

So, this year, because I am not certain if Passover is to be celebrated in March or April, I get July 3rd and July 31 for Pentecost, depending on which calendar is correct (the one that had Passover in March verses the one that the Jewish communities are using.  Also, the 18th day of the third month would be May 25 and June 22 respectively.

Now, the 18th day of the third month is interesting and "high watch day" because of what took place before Israel in Exodus 19.  The sound of a trumpet grew louder and louder, God came down to the top of the mountain, God called Moses up, and Moses went up.  Sound familiar?  A strong possibility for our rescue event.  This 18th day of the third month is about 10 days past the traditional date for Pentecost.  It is only Jewish tradition that the law which was spoken by God from Mount Sinai occurred on Pentecost.  I do not believe that idea is Biblical.

Lastly, I observed something in Paul's writings.  He is the apostle to the gentiles (that is us).  I believe he thought of himself in the role of a priest before Jesus on our behalf because of what he said in Romans 15:15-16 about his writing boldly to them, reminding them of things because the grace of God had been given to him to be a minister of Christ as a" priest" and he wanted his offering of the gentiles to become acceptable to the Father" having been sanctified by the Holy Spirit" (oil being poured on the offering).  

I wonder if Paul also thought that perhaps Jesus was going to come back to rescue the bride (receiving Paul's wave offering) on Pentecost.  The reason I am thinking this is because on his third missionary journey, while he was way out in Troas, he wanted to get back to Jerusalem quickly to be there in time for Pentecost (Acts 20:16).  On the return trip he decided to not visit Ephesus again in order to not be further delayed.  I wonder, why such a rush and focus on Pentecost?  He did not have the same feeling about Passover/Unleavened Bread.  Why?

Perhaps his focus on Pentecost is that he saw it as the time for Jesus to return and he wanted to be in Jerusalem to, in a sense, offer up the wave offering of Gentiles.

Douglas Henney