The first month of each year was Abib, meaning or having to do with ripening barley and its harvest. That was the calendar arrangement as give the ancient Jews. After their captivity in Babylon, the Hebrews have used the Babylonian word Nisan for the first month of their year. The Jews were given and used a lunar calendar, and the start of Abib of each year was observed, rather that pre-known, and based on the observable new moon and when the Barley crop was ripe. The 14 day of that month of Abib was the Passover, and could move on what we now use as our solar calendar by a little more than a month. What a wonder! I am married to a woman who never likes to do the same thing in the same way twice. Being one who likes to do the same things the exact same way for the sake of efficiency and productivity, her way drives me crazy; as mine does her. In this instance, it seems יהוה loved her way. What a wonder to have the year start at a different time each year. Knowing when Passover is and converting it onto our solar calendar can be a task!