Dear John, James, and all doves,
      Thank you James for your posting and ongoing search for eternal Truth. For an alternative interpretation of when Nisan 1 begins, I have found the articles on Passover at fossilized customs.com very useful. The articles have helped me to see that there are several considerations or variables as to when Nisan 1 begins. The state of aviv barley in Israel is only one factor to be considered.
      I believe that Nisan 1 began a few days earlier. This means that Nisan 14-15 will be on 4-18 to 19. We start as we go from 18 to 19 in Israel. The process starts with the timeline there. Add the 8 days for Passover/Unleavened Bread and we are on the timeline for Firstfruits mentioned by M.J. Agee and Sam Orlando, among others. That will be 4-26. We go through the full day 26 with the time in Israel. If we waited to see the new moon, we would be 1 or 2 days late for Passover at the full moon. We cannot delay the arrival of the full moon. Scripture tells us that Passover is at the full moon.
      James, why do you trust the opinions of Karaites on spiritual matters? These are individuals who do not trust the Christ/Messiah as personal Redeemer. Why trust 2 male witnesses thereof to see a new moon and declare it?  Declare it to whom? Themselves? There is no earthly high priest in Jerusalem to whom it can be declared! Our High Priest is in heaven. We are told in Revelation that He has all authority on earth and heaven. He knows when Nisan 1 begins. Also, there is no temple made with hands on earth in Jerusalem to whom 2 male witnesses can report anything!
      I would be very wary of giving my trust  for spiritual matters, to individuals who do not accept and declare Christ/Messiah as personal Redeemer and our only hope for forgiveness of sins and reconciliation with Abba Father. Who might a blind guide or false prophet be? Please read the articles. They will assist you and other doves in asking questions and searching more deeply for His Truth. May your searches be blessed, James, and yours dear doves. We are indeed in a season to be watching for The Groom.

With Love and Shalom,
Jean Stepnoski