When Do We Keep Passover?

Yahweh tells us to observe Passover and the Feast of Unleavened Bread. He also tells us when to keep Passover and the Feast of Unleavened Bread.
Lev 23:4 “These are the appointed feasts of Yahweh, the holy convocations, which you shall proclaim at the time appointed for them. 5 In the first month, on the fourteenth day of the month at twilight, is Yahweh’s Passover. 6 And on the fifteenth day of the same month is the Feast of Unleavened Bread to Yahweh; for seven days you shall eat unleavened bread.

Question:
  1. What month is Passover in?
  2. What day of the month is Passover in?
  3. At what time is Passover?
  4. What month and day is the Feast of Unleavened Bread?
  5. How long is the Feast of Unleavened Bread?

When is the First Month?
Deuteronomy 16:1 “Observe the month of Abib and keep the Passover to Yahweh your Elohim, for in the month of Abib Yahweh your Elohim brought you out of Egypt by night.
So, in Leviticus 23, we were told that Passover on the 14th day of the first month. We were also told to keep the Feast of Unleavened Bread on the fifteenth day of the same month. Both Passover and the Feast of Unleavened Bread are in the first month.
But when is the first month? In Deuteronomy 16, we are told that it was in the month of Abib that Yahweh brought Israel out of Egypt. So, that means that the first month and the month of Abib are the same thing. The first month of the year is the month of Abib.
Question:
  1. What is the name of the first month?
When is it the First Month?
Yahweh gave us lights in the sky to help us keep Passover and the Feast of Unleavened Bread.
Genesis 1:14 HCSB Then Elohim said, "Let there be lights in the expanse of the sky to separate the day from the night. They will serve as signs for festivals and for days and years.
Psalm 104:19 HCSB He made the moon to mark the festivals; the sun knows when to set.
How do we know when the first month is? We look at the moon.
We received our faith from those who preached to us, who got preached to…, who received it from the apostles, all the way back to faithful Adam.
1 Corinthians 11:2 Now I commend you because you remember me in everything and maintain the traditions even as I delivered them to you.
We have received that the sun determines the year, and the moon determines the month. The words for “month” and “new moon” are the same in Hebrew and sometimes the word “new moon” translates better than the word “month.”
 In Hebrew, the word for “new moon” and “month” in Hebrew is “chodesh.” Deuteronomy 16:1 is better understood when you replace the word “month” with “new moon.”
Deuteronomy 16:1 “Observe the month [new moon] of Abib and keep the Passover to Yahweh your Elohim, for in the month of Abib Yahweh your Elohim brought you out of Egypt by night.
To understand when to keep Passover, we need to know what Abib is and what the new moon of Abib is.
What is Abib and What is the New Moon of Abib?
To understand when to keep Passover, we also need to go to the first Passover. When we see when Moses and the Israelites kept Passover, then we also can know when to keep Passover.
Question:
  1. How many plagues did Egypt suffer?
  2. What was the seventh plague?
  3. What was the eight plague?
  4. What the ninth plague?
  5. What was the tenth plague?
We are introduced to Abib during the seventh plague.
Exodus 9:23 Then Moses stretched out his staff toward heaven, and the LORD sent thunder and hail, and fire ran down to the earth. And the LORD rained hail upon the land of Egypt.
31 (The flax and the barley were struck down, for the barley was in the ear [Abib] and the flax was in bud. 32 But the wheat and the emmer were not struck down, for they are late in coming up.)
“In the ear” is “abib”. The definition for abib from Strong’s Concordance is (1) fresh, young ears, also (2) Canaanite name for the first month of the Jewish calendar.
“Abib” means the barley was ripe and fresh. It is not ready to be harvested though. The ripening of the barley takes place in the spring.
The ripening of the barley is a result of the changing of the seasons, which is caused by the sun. Yahweh told us that He gave us the lights in the heavens for festivals, days and years. So, we follow the sun, and not the barley ripening, to know when the year has begun. Yahweh said the sun, moon, and stars, are available to everyone.
Deuteronomy 4:19 And beware lest you raise your eyes to heaven, and when you see the sun and the moon and the stars, all the host of heaven, you be drawn away and bow down to them and serve them, things that Yahweh your Elohim has allotted to all the peoples under the whole heaven.
A Different Calendar
The United States and most of the world use a calendar called the Gregorian calendar. The Gregorian calendar uses only the sun to determine the years and the months. Months are simply divisions of the year. The moon does not matter at all in the Gregorian calendar.
Yahweh’s calendar is different from the Gregorian calendar. Yahweh’s calendar uses both the sun and the moon. The sun determines the years, and the moon determines the months.
It takes the earth 365.25 days to go around the sun. That is the length of one year. The moon takes 27.322 days (space.com) to go around the earth. That is the length of one month in Yahweh’s calendar.
Observe that dividing one year by one month does not give a whole number. 365.25 / 27.322 = 13.3683. That means that months and years will not start at the same time.
Because Yahweh’s calendar uses both the sun and the moon. The sun determines the years, and the moon determines the months, and the year is not divisible by the months, then in the year and months can begin at different times. We see exactly that occurrence leading up to the first Passover.
During the seventh plague, it was recorded that the barley was abib (Exodus 9:31). That means the year had begun. But the months of the new year did not begin until Exodus 12:1-2 [most likely a few weeks later] when Yahweh shows Moses a new moon and tells Moses to mark that new moon as the first new moon of the year. That new moon was the first new moon after abib was noticed. That is the new moon that Yahweh calls the new moon [and month] of Abib in Deuteronomy 16:1.
Exodus 12:1-2 Yahweh said to Moses and Aaron in the land of Egypt, 2 “This new moon shall be for you the beginning of new moons. It shall be the first new moon of the year for you.
Then Yahweh told Moses and Aaron to tell people to start preparing for the Passover and the Feast of Unleavened Bread.
3 Tell all the congregation of Israel that on the tenth day of this new moon every man shall take a lamb according to their fathers’ houses, a lamb for a household. 4 And if the household is too small for a lamb, then he and his nearest neighbor shall take according to the number of persons; according to what each can eat you shall make your count for the lamb. 5 Your lamb shall be without blemish, a male a year old. You may take it from the sheep or from the goats, 6 and you shall keep it until the fourteenth day of this new moon, when the whole assembly of the congregation of Israel shall kill their lambs at twilight.
17 And you shall observe the Feast of Unleavened Bread, for on this very day I brought your hosts out of the land of Egypt. Therefore you shall observe this day, throughout your generations, as a statute forever. 18 In the first new moon, from the fourteenth day of the new moon at evening, you shall eat unleavened bread until the twenty-first day of the new moon at evening.
So, to determine when Passover and Unleavened Bread begin:
  1. Find the beginning of spring. Usually March 20th, 21st, or 22nd.
  2. Find the first new moon after that. That would be first day of the first month.
  3. Count from the first day to the fourteenth day. At twilight would be Passover. At sunset would be first day of Unleavened Bread.