Most people to this day celebrate Passover according to Hillel's calendar, which was made in the fourth century for observing Yahveh's Festivals all over the world. With Jews moving everywhere and no communication to know when the New Moon sightings and the Aviv Barley coincided, this calendar has served all for many centuries.

However, today we have instant communication all over the world, and we can know the exact day, as set by Yahveh at Exodus to observe this Feast. The correct day for observing the Passover is determined by the sighting of the new moon and the "Aviv" barley, when the barley is ready for harvest.  The correct date is not a Salvation issue. Our attempt to do it right is between us and Yahveh. I am passing this along for your edification, should you 'stray' from traditional observance to the proper day according to Yahveh and the way He instituted Passover for all generations.

These links will help to understand how the Biblical correct day is now possible. Whatever day you choose, here is hoping you enjoy the celebration of  Hag Ha-Matzot ~ The Feast of Unleavened Bread.

Teachings - The Biblical Hebrew Calendar <http://6001.com/calend.htm>
The Month of Aviv <http://6001.com/cal_art4.htm>
Biblical Passover Haggadha New <http://www.karaite-korner.org/rekhavi/haggadha.shtml>