Did the Hebrew day begin in the morning or evening?

Modern Jews start a new day at sunset. It is thought that this calendar convention also existed at the time of Jesus although there may have been more than one calendar at that time with different sects giving preference to one over another.

Genesis 1 describes the completion of each day's creative acts by God with the words: there was evening and there was morning, the nth day. Some commentators have argued that the day began at evening and Genesis is saying that the beginning of the day is at evening, then morning occurred, and the day therefore ended at the next evening. This sounds strained. Evening and morning occur after the creative act. It seems more logical to read the verses as saying that the creative acts occurred during the daylight followed by evening after the creative acts have finished* followed by night followed by the next morning which is the terminus of the day.

And God said, “Let the waters swarm with swarms of living creatures, and let birds fly above the earth across the expanse of the heavens.” So God created the great sea creatures and every living creature that moves, with which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good. And God blessed them, saying, “Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth.” And there was evening and there was morning, the fifth day. (Gen 1:20-23)

The day begins at dawn, then God creates the fish and birds, then the evening comes, and then the day completes with a new morning.

I suspect that this was the case at creation and was still in place at the time of the Exodus. That is, the Hebrew day started at dawn and finished the following dawn. A transition to a calendar where the day commences at dusk occurred sometime later: prior to the current era, possibly before the time of Jesus; perhaps around the time of the Exile to Babylon. There is evidence of a different possible calendar change at the time of the Exile: the year start switched from the first month (Nisan) to the seventh month (Tishri).

If the day started at dawn, at least from the time of creation to the exodus, there could be evidence of this in Scripture.

I would argue that the instructions concerning Passover and Unleavened Bread make the most sense if the day commenced at dawn. I will call a day commencing at dawn a dawn-day. That is, at dawn when the sun comes up a new day begins. Likewise dusk-days commence in the evening.

English Bibles often use the term "twilight" whereas the literal text uses the phrase "between the evenings". There is considerable debate about what this phrase means. It may be that the first evening occurs when the sun goes down and the second evening when it gets dark. Or from sundown to midnight. Or from noon until sundown. Perhaps even between noon and midnight. For the passages we will discuss the interpretation does not significantly affect our calculations.

There are three instructions concerning the Passover and the Feast of Unleavened Bread. These occur in Exodus, Leviticus and Numbers. These instructions were all given during the same epoch which means that the time the day began was almost certainly the same for all three episodes. This is unless Exodus uses an Egyptian calendar which changed after the Hebrews left Egypt.

God gave Moses instructions for the Passover,

Yahweh said to Moses and to Aaron in the land of Egypt, saying, “This month [Abib, Nisan] will be the beginning of months; it will be for you the first of the months of the year. Speak to all the community of Israel, saying, ‘On the tenth of this month, they will each take for themselves a lamb for the family,...

“You will keep it until the fourteenth day of this month, and all the assembly of the community of Israel will slaughter it between the evenings... And they will eat the meat on this night;...

“And I will go through the land of Egypt during this night, and I will strike all of the firstborn in the land of Egypt,...

“And this day will become a memorial for you, and you will celebrate it as a religious feast for Yahweh throughout your generations; you will celebrate it as a lasting statute. You will eat unleavened bread for seven days. Surely on the first day you shall remove yeast from your houses, because anyone who eats food with yeast from the first day until the seventh day—that person will be cut off from Israel. It will be for you on the first day a holy assembly and on the seventh day a holy assembly; no work will be done on them; only what is eaten by every person, it alone will be prepared for you.

“And you will keep the Feast of Unleavened Bread, because on this very day I brought out your divisions from the land of Egypt, and you will keep this day for your generations as a lasting statute. On the first day, on the fourteenth day of the month, in the evening, you will eat unleavened bread until the evening of the twenty-first day of the month. For seven days yeast must not be found in your houses, because anyone eating food with yeast will be cut off from the community of Israel—whether an alien or a native of the land. You will eat no food with yeast; in all of your dwellings you will eat unleavened bread.” (Exo 12)

Passover was on the fourteenth day of Nisan. The Feast of Unleavened Bread was for seven days. They were to start eating the unleavened bread on the evening of Nisan 14 and continue until the evening of Nisan 21.

In Leviticus God gives further instructions,

These are Yahweh’s appointed times, holy assemblies, which you shall proclaim at their appointed time. In the first month, on the fourteenth of the month at the evening is Yahweh’s Passover. And on the fifteenth day of this month is Yahweh’s Feast of Unleavened Bread; for seven days you shall eat unleavened bread. On the first day there shall be a holy assembly for you; you shall not do any regular work. And you shall present an offering for Yahweh made by fire for seven days; on the seventh day there shall be a holy assembly; you shall not do any regular work. (Lev 23:4-8)

This reiterates the command in Exodus but clarifies that Passover is on Nisan 14 and the Feast of Unleavened Bread begins on Nisan 15. Exodus states that unleavened bread is to be eaten from Nisan 14, that is from Passover proper; yet they are to eat it for 7 days. Leviticus states that the Feast of Unleavened Bread proper starts on Nisan 15.

Again, in Numbers, at the end of 40 years of wandering, God commands,

On the fourteenth day of the first month is the Passover for Yahweh. On the fifteenth day of this month is a religious feast, unleavened bread must be eaten for seven days. On the first day there will be a holy assembly you will not do any regular work.... On the seventh day you will have a holy assembly you will not do any regular work. (Num 28:16-18,25)

These passages give similar commands. What is notable is that while all three give 7 days as the duration of the Feast of Unleavened Bread, Exodus specifies that this is to be from the evening of Nisan 14 to the evening of Nisan 21. There is also to be a holy assembly on the first and seventh days of Unleavened Bread.

Using dawn-days we have Nisan 14 starting in the morning and the passover lamb being killed between the evenings (ʿereb) and eaten that night (layil). Unleavened bread would be eaten that evening with the Passover meal (Exo 12:8,18). The following morning starts the next day: Nisan 15. Nisan 15 is the first day of the Feast of Unleavened Bread when they have a holy assembly with the attendant sacrifices. Nisan 16 is day 2 of the feast, Nisan 21 is day 7. There is a holy assembly that day also. In the evening the feast ends and unleavened bread only needs to be eaten until that evening (Exo 12:18).

Date	Time	Feast day	Comments
Nisan 14	morning
	evening	Passover sacrifice	unleavened bread begins
Nisan 15	morning	Feast Day 1	holy assembly
	evening
Nisan 16	morning	Feast Day 2
	evening
Nisan 17	morning	Feast Day 3
	evening
Nisan 18	morning	Feast Day 4
	evening
Nisan 19	morning	Feast Day 5
	evening
Nisan 20	morning	Feast Day 6
	evening
Nisan 21	morning	Feast Day 7	holy assembly
	evening		unleavened bread ends
Nisan 22	morning

Using dusk-days the entire feast of Passover and Unleavened Bread must last 8 days. Nisan 13 changes to Nisan 14 at dusk. The lamb is slaughtered and eaten that night along with unleavened bread. In the morning it is still Nisan 14 which is still Passover day. The Feast of Unleavened Bread does not start until that evening Nisan 15 (Lev 23:6). The holy assembly occurs that day but not until the following morning because they were not to work and the sacrifice of the first day of Unleavened Bread occurs at the same time as the morning sacrifice (Num 28:23).

Nisan 15 is the first day of the feast and Nisan 21 the seventh day. Nisan 21 starts in the evening but the evening of Nisan 21 is also when the the consumption of unleavened bread ceased. From the evening of Nisan 21 the Israelites were no longer required to eat unleavened bread even though the Feast of Unleavened Bread still had one day to go. The following morning they had the holy assembly on the final day of the feast. If unleavened bread was to be continued to be eaten until the end of Nisan 21, just before Nisan 22 started, then the command to eat for seven full days (Exo 12:19) is actually eight full days. 

Date	Time	Feast day	Comments
Nisan 14	evening	Passover sacrifice	unleavened bread begins
	morning
Nisan 15	evening	Feast Day 1
	morning		holy assembly
Nisan 16	evening	Feast Day 2
	morning
Nisan 17	evening	Feast Day 3
	morning
Nisan 18	evening	Feast Day 4
	morning
Nisan 19	evening	Feast Day 5
	morning
Nisan 20	evening	Feast Day 6
	morning
Nisan 21	evening	Feast Day 7	unleavened bread ends
	morning		holy assembly
Nisan 22	evening

All three passages concerning Passover and the Feast of Unleavened Bread make sense if the Israelites were using dawn-days. Dusk-days imply that there is a morning after Passover begins prior to the holy assembly, and that the second holy assembly occurs after the time of unleavened bread ceases.

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*This may not be the case on day 2.

Why does the Easter date vary so much?

In the Western church (Catholic and Protestant churches) Easter occurs on the first Sunday after the first full moon after the Spring Equinox. Spring equinox occurs around March 21 but can occur a day earlier. For the church's purposes the equinox occurs March 21. The full moon can occur from March 21 and up to 29 days later.

The Eastern* church (Orthodox church) uses a similar formula but follows the older Julian calendar, and defines certain days. Thus "full moon" occurs on the 14th day of the month, not when the moon is full.

Jesus died at Passover. Passover begins Nisan 14† which is during the first month of the Jewish year. The Jewish calendar is lunar-solar which means that the months all begin at the new moon. Months are 29 or 30 days long. Because there are more than 12 lunar months in a year the Jewish year occasionally has an extra month. The Jewish New Year starts about the time of the spring equinox (northern hemisphere).

So Jesus was crucified on a Friday during a full moon. The Easter date is designed to have Good Friday and Easter Sunday land close to the first full moon after the spring equinox (which approximates the Jewish New Year) while maintaining the days of the week so that every year the crucifixion and resurrection days land on Friday and Sunday respectively.

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*Some Eastern churches use the Western date.
†Modern Jews use Nisan 15.

Chronology of the Flood

Genesis specifies several dates during the year of the Flood. Noah and his family entered the Ark in the 600th year of Noah's life: year 1656 Anno Mundi.

They entered on the 17th day of the second month and the waters prevailed 150 days until the 17th day of the 7th month; thus making 5 months equal to 150 days therefore each month 30 days in length*.

Here is the chronology of the Flood taken from Genesis 7–8.

Event	Month	Day	Day count
			Exclusive	Inclusive
Enter the Ark	2	17	0	1
1 month	3	17	30	31
Rain ceases (inclusive)	3	26		40
Rain ceases (exclusive)	3	27	40
2 months	4	17	60	61
3 months	5	17	90	91
4 months	6	17	120	121
Ark rests	7	17	150	151
6 months	8	17	180	181
7 months	9	17	210	211
Mountains visible	10	1	224	225
8 months	10	17	240	241
Send raven	11	11	264	265
9 months	11	17	270	271
10 months	12	17	300	301
Waters dried up	1	1	314	315
11 months	1	17	330	331
12 months	2	17	360	361
Earth dry, leave Ark	2	27	370	371

It seems that the Bible more frequently uses inclusive reckoning, either way they spend 371 days inside the Ark. While I have known of this number for some years, I noticed it coincided with the duration of a solar year based on a 30-day month with an altered earth spin as per my previous calculations. This seems a little more than coincidental. If this were the case perhaps the Noadhic calendar was a lunar-solar calendar similar to the Hebrew calendar and various other calendars.

A lunar-solar calendar aligns the months with the moon (new moon to new moon) and has a variable number a months to keep the seasons aligned. That is 12 months each year with an extra month approximately every 3 years (both antediluvian and postdiluvian solar years have a surplus of ~11 days over the lunar year).

The antediluvian lunar-solar calendar would have 12 30-day months for a 360-day year. The postdiluvian lunar-solar calendar has ~29.5-day months, thus alternating between 29- and 30-day months, but depending on when the new moon appears, for a 354-day year.

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*This seems to be the most likely interpretation but the weather may have precluded accurate visualisation of the moon and 30-day months may have been used until adequate moon sighting allowed resetting of the calendar. The second option raises the question as to why not use alternating 29 and 30 day months until the calendar could be corrected.

The length of the antediluvian month and year

If the earth's spin increases then the days in a year increases. The year—as measured in a stable time metric, such as atomic-seconds—is unchanged because it is dependant on the distance from the sun, but the year as measured in days does change because the length of the day is dependant on the spin. The same can be said about the month.

If we define the year length to be y in unchanging units; the day to be d_a for the antediluvian day and d_p for the postdiluvian day; n_a is number of days in an antediluvian year and n_p the number of days in a postdiluvian year; then

d_a × n_a = y = d_p × n_p

d_a = d_p × n_p/n_a

d_p/d_a = n_a/n_p

Many ancient calendars use 360 days for a year. Perhaps these are stylised, especially as these calendars are postdiluvian; but what if they were based on memory of an antediluvian year of such a length? In such a case the length of an antediluvian day would have been

d_a = 24 hours × 365.25/360 = 24 hours 21 minutes.

We will define a month to be m in unchanging units and the number of days in an antediluvian month k_a; then

d_a × k_a = m = d_p × k_p

k_a = k_p × d_p/d_a = k_p × n_a/n_p

d_p/d_a = k_a/k_p = n_a/n_p

If a (synodic) month is now 29.53 days (new moon to new moon)

d_p = 24 hours, k_p = 29.53 days

then the antediluvian month (assuming a 360-day year) was

k_a = 29.5 days × 360/365.25 = 29.1 days

Now consider instead if the antediluvian month was 30 days in length

k_a = 30 days, k_p = 29.53 days

then the antediluvian day was

d_a = d_p × k_p/k_a = 24 × 29.53/30 = 23 hours 38 minutes

and the antediluvian year was

n_a = n_p × k_a/k_p = 365 × 30/29.53 = 371 days

These calculations assume no change in distance from the earth to the sun or the moon.

Sinking mantle

Some years back Stripe recommended the video series by Calvary Chapel on earthquakes. 2 sermons about an hour each in 6 or 7 parts. Part 2 is more interesting. Kevin Lea defends Walt Brown's Hydroplate Theory.

The theory as it applies to the Flood is that the earth had significant water below the crust which was released through the crust along the midatlantic ridge (and around the earth) causing flooding and a contra-spherical depression which became the pacific basin. Importantly the model specifies that the continents moved over the mantle due to gravity until they struck opposition which led to upfaulting (mountains) and downfaulting (trenches). The model does not claim that some plates are subducting over or under other plates, though these regions represent real faults. Thus the Hydroplate Theory is distinct from Baumgardner's Catastrophic Plate Tectonic Model.

The relationship to earthquakes is the theory's claim that the inside of the earth consisted of a solid mantle but no core prior to the flood. As a result of stresses within the mantle, rock melts then rises or sinks depending on the surrounding pressure and resultant density. Lower pressure shallow mantle expands and decreases density when it melts therefore rises; high pressure deep mantle shrinks and increases density when it melts therefore sinks. The depth at which mantle changes from expanding to shrinking is called the transition zone. These changes in density and volume mean that other mantle surrounding it moves and the transmitted movement is felt as an earthquake. Rising melted mantle also surfaces in volcanic eruptions.

There is more detail than this; I have not read Brown's book, this is what I gleaned from the video.

Of interest is that because mantle melts and shrinks at certain depths, it must sink and cannot rise. So it will form a core. A liquid core with (the relatively) lower pressures and resolidifying to form a solid core with higher pressures. This results in an inner solid core and outer liquid core which can only grow as mantle continues to melt, shrink, and then sink to the core. Because it has shrunk (increased density) the volume of the earth must decrease. This seems to be the case concerning the mantle regardless of whether the hydroplate model is correct: every time mantle rock melts below the transition zone it sinks to the core never to rise again.

On hearing this my first thought was if the volume of the earth shrinks then its spin will increase (assuming no change in mass) due to conservation of angular momentum. The speaker subsequently discussed this same issue.

If there were significant changes at the time of the Flood this could alter the measured duration of the year and month. More on this to come.

The timing of the Passover and the Feast of Unleavened Bread

God gave the Israelites specific commands concerning the celebration of the Passover and the associated Feast of Unleavened Bread. The Passover was instituted at the time God delivered the Israelites from Egypt. The month of Nisan (Abib) in the Spring became the first month of the year for the Hebrews. Every household was to take one lamb on the 10th day of the month and kill it on the 14th of the month.

Your lamb shall be without blemish, a male a year old. You may take it from the sheep or from the goats, and you shall keep it until the fourteenth day of this month, when the whole assembly of the congregation of Israel shall kill their lambs at twilight (between the evenings). (Exodus 12:5-7)

Twilight being the time between sundown and the sky turning black. The sky remains lit for a short time after the sun disappears over the horizon. By the time of the New Testament it appears that the Jews considered that the new day commenced at the beginning of twilight; modern Judaism still starts the day at sundown. It seems to me, during the time of the Torah at least, that the new day started at dawn. There are several reasons to think this though I will not address them here, I will continue on the assumption of a new day starting at dawn.

Celebration	Day	Date
Passover	0	Nisan 14
Unleavened Bread	1	Nisan 15
Unleavened Bread	2	Nisan 16
Unleavened Bread	3	Nisan 17
Unleavened Bread	4	Nisan 18
Unleavened Bread	5	Nisan 19
Unleavened Bread	6	Nisan 20
Unleavened Bread	7	Nisan 21

Leviticus reiterates that the lamb is to be killed on the 14th day.

In the first month, on the fourteenth day of the month at twilight, is the Lord's Passover. And on the fifteenth day of the same month is the Feast of Unleavened Bread to the Lord; for seven days you shall eat unleavened bread. On the first day you shall have a holy convocation; you shall not do any ordinary work. But you shall present a food offering to the Lord for seven days. On the seventh day is a holy convocation; you shall not do any ordinary work.” (Leviticus 23:5-8)

Numbers repeats the command prior to the second Passover 1 year after leaving Egypt.

Let the people of Israel keep the Passover at its appointed time. On the fourteenth day of this month, at twilight, you shall keep it at its appointed time; according to all its statutes and all its rules you shall keep it.” So Moses told the people of Israel that they should keep the Passover. And they kept the Passover in the first month, on the fourteenth day of the month, at twilight, (Numbers 9:2-5)

The first Passover occurred on Nisan 14 at twilight. The firstborn were killed at midnight (Exo 12:29) still the 14th day of Nisan. Pharaoh summoned Moses and told him to leave. The Egyptians also urged the Israelites to leave. They set out that morning.

They set out from Rameses in the first month, on the fifteenth day of the first month. On the day after the Passover, the people of Israel went out triumphantly in the sight of all the Egyptians, while the Egyptians were burying all their firstborn, whom the Lord had struck down among them. On their gods also the Lord executed judgments. (Numbers 33:3-4)

So they set out in the morning when the new day commenced, that is Nisan 15. The bread was not risen due to the haste at which the Israelites left (Exo 12:39). God also instituted the Feast of Unleavened Bread at this time.

This day shall be for you a memorial day, and you shall keep it as a feast to the Lord; throughout your generations, as a statute forever, you shall keep it as a feast. Seven days you shall eat unleavened bread. On the first day you shall remove leaven out of your houses, for if anyone eats what is leavened, from the first day until the seventh day, that person shall be cut off from Israel. On the first day you shall hold a holy assembly, and on the seventh day a holy assembly. No work shall be done on those days. But what everyone needs to eat, that alone may be prepared by you. 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. In the first month, from the fourteenth day of the month at evening, you shall eat unleavened bread until the twenty-first day of the month at evening. For seven days no leaven is to be found in your houses. If anyone eats what is leavened, that person will be cut off from the congregation of Israel, whether he is a sojourner or a native of the land. You shall eat nothing leavened; in all your dwelling places you shall eat unleavened bread. (Exodus 12:14-20)

You shall keep the Feast of Unleavened Bread. Seven days you shall eat unleavened bread, as I commanded you, at the time appointed in the month Abib, (Exodus 34:18)

Therefore unleavened bread was to be eaten from the evening of the 14th until the evening of the 21st, but not necessarily during the day of the 14th prior to twilight, or after sunset on the 21st. The Israelites were to eat bread without yeast at the Passover meal and during the days of Unleavened Bread but it does not appear to be that the yeast was to be removed from the dwelling until the 1st day of Unleavened Bread, that is Nisan 15.

On the 1st day of Unleavened Bread (15th) there was to be a feast, and also on the last day (21st).

Then Moses said to the people, “Remember this day in which you came out from Egypt, out of the house of slavery, for by a strong hand the Lord brought you out from this place. No leavened bread shall be eaten. Today, in the month of Abib, you are going out. And when the Lord brings you into the land of the Canaanites, the Hittites, the Amorites, the Hivites, and the Jebusites, which he swore to your fathers to give you, a land flowing with milk and honey, you shall keep this service in this month. Seven days you shall eat unleavened bread, and on the seventh day there shall be a feast to the Lord. Unleavened bread shall be eaten for seven days; no leavened bread shall be seen with you, and no leaven shall be seen with you in all your territory. You shall tell your son on that day, ‘It is because of what the Lord did for me when I came out of Egypt.’ And it shall be to you as a sign on your hand and as a memorial between your eyes, that the law of the Lord may be in your mouth. For with a strong hand the Lord has brought you out of Egypt. You shall therefore keep this statute at its appointed time from year to year. (Exodus 13:3-10)

Both the 1st day (15th) and the 7th day (21st) were to be a holy convocation, that is, there was to be no work done.

On the fourteenth day of the first month is the Lord's Passover, and on the fifteenth day of this month is a feast. Seven days shall unleavened bread be eaten. On the first day there shall be a holy convocation. You shall not do any ordinary work, but offer a food offering, a burnt offering to the Lord: two bulls from the herd, one ram, and seven male lambs a year old; see that they are without blemish; also their grain offering of fine flour mixed with oil; three tenths of an ephah shall you offer for a bull, and two tenths for a ram; a tenth shall you offer for each of the seven lambs; also one male goat for a sin offering, to make atonement for you. You shall offer these besides the burnt offering of the morning, which is for a regular burnt offering. In the same way you shall offer daily, for seven days, the food of a food offering, with a pleasing aroma to the Lord. It shall be offered besides the regular burnt offering and its drink offering. And on the seventh day you shall have a holy convocation. You shall not do any ordinary work. (Numbers 28:16-25)

Further, there were to be special sacrifices to God during this festival. It was one of the 3 main festivals for Israel: the Feast of Unleavened Bread, the Feast of Harvest (Weeks), and the Feast of Ingathering (Booths).

“Three times in the year you shall keep a feast to me. You shall keep the Feast of Unleavened Bread. As I commanded you, you shall eat unleavened bread for seven days at the appointed time in the month of Abib, for in it you came out of Egypt. None shall appear before me empty-handed. (Exodus 23:14-15)

It is notable that the Passover could not be eaten by anyone who was unclean. For those who had become unclean Passover was deferred for 1 month.

And there were certain men who were unclean through touching a dead body, so that they could not keep the Passover on that day,... The Lord spoke to Moses, saying, “Speak to the people of Israel, saying, If any one of you or of your descendants is unclean through touching a dead body, or is on a long journey, he shall still keep the Passover to the Lord. In the second month on the fourteenth day at twilight they shall keep it. They shall eat it with unleavened bread and bitter herbs. (Numbers 9:6-11)

Moses repeated the instructions concerning the Passover and the Feast of Unleavend Bread during his sermon prior to entering Canaan.

Observe the month of Abib and keep the Passover to the Lord your God, for in the month of Abib the Lord your God brought you out of Egypt by night. And you shall offer the Passover sacrifice to the Lord your God, from the flock or the herd, at the place that the Lord will choose, to make his name dwell there. You shall eat no leavened bread with it. Seven days you shall eat it with unleavened bread, the bread of affliction—for you came out of the land of Egypt in haste—that all the days of your life you may remember the day when you came out of the land of Egypt. No leaven shall be seen with you in all your territory for seven days, nor shall any of the flesh that you sacrifice on the evening of the first day remain all night until morning. You may not offer the Passover sacrifice within any of your towns that the Lord your God is giving you, but at the place that the Lord your God will choose, to make his name dwell in it, there you shall offer the Passover sacrifice, in the evening at sunset, at the time you came out of Egypt. And you shall cook it and eat it at the place that the Lord your God will choose. And in the morning you shall turn and go to your tents. For six days you shall eat unleavened bread, and on the seventh day there shall be a solemn assembly to the Lord your God. You shall do no work on it. (Deuteronomy 16:1-8)

Again we read the Passover is to occur at twilight, they are not to eat leaven for 7 days. They are to go to there tents in the morning after Passover, that is Nisan 15, day one of the Feast of Unleavened Bread, and eat unleavened bread for 6 days inclusive, Nisan 15 to Nisan 20, and hold a holy convocation on day 7, Nisan 21.

On entering Canaan under Joshua they celebrated the Passover

While the people of Israel were encamped at Gilgal, they kept the Passover on the fourteenth day of the month in the evening on the plains of Jericho. And the day after the Passover, on that very day, they ate of the produce of the land, unleavened cakes and parched grain. And the manna ceased the day after they ate of the produce of the land. And there was no longer manna for the people of Israel, but they ate of the fruit of the land of Canaan that year. (Joshua 5:10-12)

To summarise

• The day commenced at sunrise
• A lamb was selected on Nisan 10
• Passover occurred on Nisan 14
• The passover lamb was killed at twilight and eaten with bitter herbs and unleavened bread
• No yeast was to be eaten from twilight Nisan 14 until twilight Nisan 21
• The Feast of Unleavened Bread began on Nisan 15
• The dwelling was cleared of all yeast on Day 1 of the Feast of Unleavened Bread, Nisan 15
• A holy convocation was held on Day 1, Nisan 15
• A feast was held on Day 1, Nisan 15
• Sacrifices were made on Day 1 thru Day 7, Nisan 15 to Nisan 21
• A holy convocation was held on Day 7, Nisan 21
• A feast was held on Day 7, Nisan 21

Has the year always been the same duration?

There are some writings that claim that the year was previously shorter than it is now. Some people have suggested the year has been 360 days long in the past. Velikovsky mentions a myth that says 5 days were taken from the moon and given to the sun. That is the previous lunar year was 12 × 30 (= 360) days and the old solar year was 360 days. The current lunar year is now 354 and a bit days, solar year 365 and a bit.

Some suggest that the year may have been even shorter prior to this.

If the year has been of different duration (measured in days) there are 2 options:
Scenario 1. The earth's spin was previously slower and has since speed up. Scenario 2. The earth's orbit was previously closer to the sun.

Of course it could be a combination of the 2.

Scenario 1
If the earth's spin was slightly slower and has speed up (presumably by a factor of ~365/360) then the absolute duration of the year is unchanged but more days pass in a year because the days are now shorter.

Scenario 2
If the day length is unchanged then a shorter year would be absolutely shorter, the duration of the year is related to the distance from the earth to the sun (and eccentricity of the orbit, though the earth's orbit is close to circular)

The month is currently 29.5 days long. Scenario 2 with an altered earth orbit would have a shorter year but the same duration of the month. Scenario 1 would have a longer old day of 24.35 hours (360/365.25×24) which would make the previous month seem shorter at 29 old days rather than the 29.5 days it currently is. Of course the orbit of the moon could have changed at the same time (or at another time). The asymmetrical cratering of the moon suggests catastrophe in the heavens.

An idea that came to me reading a footnote in the book In the Beginning: Compelling Evidence for Creation and the Flood by Walt Brown. I have not actually read the book so this may have been in the book, nevertheless I have not seen it previously: If the atmosphere pre-flood had a lot of water in it to precipitate (eg. vapour canopy theory), it would have some mass. After the flood the mass would now be at sea level, and by conservation of angular momentum, the earth would speed up, the amount depending on the height from which it precipitated. Consequently shortening the day and "lengthening" the year (in number of days).

It would be interesting to look into this in terms of the amount of water and the original height of the water. The mass may be completely insignificant and the change in spin speed inconsequential, but I haven't seen figures.

Of course any change in the earth's year may be unrelated to this and be all to do with the earth's interaction with the moon and other celestial phenomenon. Or the change in year length may have been at a different time than the flood: note Joshua's long day and Hezekiah's sundial. Or perhaps there was more than one episode.

Or course the duration of the day and the month may have been the same as the current figures since creation. It does make one wonder why the ancients had stories to the contrary though.