The month of Abib is the month where the equinox (Where the day and night are equal in length) falls on or before the 1st day of the 1st month (which occurs around March 20th upon the Gregorian calendar) .
The commandment to keep the feast “at the time appointed in the month Abib [Nisan]” (Exodus 23:15), means that the calendar must keep Abib as close as possible to spring (today we call it the “Vernal Equinox”), and then the moed of Passover can happen. Thus, the month of Abib is the month when Passover falls on or after the Vernal Equinox.
2 “This month shall be the beginning of months to you; it is to be the first month of the year to you.
3 Moses said to the people, “Remember [solemnly observe and commemorate] this day on which you came out of Egypt, out of the house of bondage and slavery; for by a strong and powerful hand YHWH brought you out of this place. And nothing leavened shall be eaten. 4 On this day in the month Abib, you are about to go onward.
7 Unleavened bread shall be eaten throughout the seven days; no leavened bread shall be seen with you, nor shall there be leaven within the borders of your territory. 8 You shall explain this to your son on that day, saying, ‘It is because of what YHWH did for me when I came out of Egypt.’ 9 It shall serve as a sign to you on your hand (arm), and as a reminder on your forehead, so that the instruction (law) of YHWH may be in your mouth; for with a strong and powerful hand YHWH brought you out of Egypt. 10 Therefore, you shall keep this ordinance at this time from year to year.
2 “The sons of Israel are to keep the Passover at its appointed time.3 On the fourteenth day of this month at twilight, you shall keep it at its appointed time; according to all its statutes and ordinances you shall keep it.”
The spring equinox currently occurs each year around March 20th or 21st upon the Gregorian calendar, and is the time when day and night are of approximately equal length. This is a solar phenomenon nut a lunar one, hence why it is called a luni-solar calendar.
Again. It is the Light which tells us His appointed times, the days and the years.
14 Then Elohim said, “Let there be light-bearers (sun, moon, stars) in the expanse of the heavens to separate the day from the night, and let them be useful for signs , and for marking appointed times, and for days, and for YEARS;
Some may wonder why it matters when Abib occurs. One reason why Abib should be assigned to the first qualifying month relative to the equinox is that there needs to be a consistency between years so that crops will be in approximately the same stage of development at the same time each year. The importance of the maturity of grain for the wave-sheaf offering (Lev. 23:9-14) is obvious.
Astronomers of ancient Babylon discovered that in the span of 19 solar years, there were exactly 235 complete lunar months. (“Exact” here means to within about 2 hours – pretty remarkable.) If one counted the 19 solar years and the “lunar years” of 12 months by counting new moons, they’d see that in “lunar years” 19 solar years is the same as 19 years and 7 months by the moon. The astronomer Meton, about 432 BCE wrote that if an intercalary month was added to the lunarcalendar 7 times in 19 years, then at the end of the 19 solar years, the number of lunar years would exactly match – i.e., 19 solar years = 19 lunar years. Meton laid out a “schedule” of when the additional month should be added. He said the leap years would be years 3, 6, 8, 11, 14, 17, and 19. (You can see the sequence of years the extra month is added: 3, 3, 2, 2, 3, 3, 2.)
This is all well and good – mathematically. But in reality, if you actually used the moon to indicate which year should be the leap year, the “schedule” of intercalary months may instead need to be (for example) years 3, 5, 7, 10, 13, 16, 19. The real moon simply does not follow a repeating 3, 3, 2, 2, 3, 3, 2 cycle. And this is the problem with 2016. According to the real moon, 2015-2016 (the current year) does not need to be a leap year, while the next Hebrew year (2016-2017) does need to be a leap year. But the traditional Hebrew calendar, with its rigid, preplanned schedule of leap years, ignores the real moon and inserts the leap month of Adar I,by schedule, into the 2015-2016 calendar year when it is not needed.
The rigid application of the Metonic cycle without regard to the “real” moon is the major problem with the 2016 traditional Hebrew calendar which applies an unnecessary leap month manifested in February, 2016. That unnecessary month causes all the Holy Days for 2016 in the traditional calendar to be one month late. The many other problems with the modern traditional calendar include the use of the “molad” of the moon, which is an “average” lunar month which sometimes causes the 1st of the month to be a day early or a day late, and the rules for “postponement” where the 1st of Tishri is held 1, 2, or 3 days so Yom Kippur will not fall on a Friday or a Sunday. We believe the use of the “average moon” to calculate the 1st day of the month is wrong. We also believe the “postponement” rules are wrong, as they are simply not scriptural.
(Note: Since writing this I have learnt that the calendar shall be restored, so much of this discussion is now obsolete. To understand what I mean, click here and read the four articles on this subject. The way in which the new year is timed however, shall remain the same)