The 13th Month of the Biblical Calendar

--[ 21 MIN READ]

The Precision of the Lunisolar Calendar

The Creator’s calendar is not a solar calendar; it is a luni-solar calendar that connects lunar months with a solar year. An average lunar year is about 354 days, which is 11 days shorter than the 365-day solar year. This difference causes strictly lunar calendars, like the Muslim Hijri calendar, to shift backward through the year. For example, Ramadan happens earlier each year because of this shifting.

In contrast, luni-solar calendars anchor the shorter lunar year to a specific point in the solar year. To maintain this alignment, a thirteenth month is naturally added seven times in a nineteen year cycle, creating a year with 13 months that compensates for the lost days. The Biblical calendar uses the vernal (spring) equinox as its anchor point, with the New Year starting on the New Moon after that equinox.

Calendars around the world that follow the Biblical Calendar, such as those used by the ancient Chinese and Babylonians, do not require a man-made leap year. The Almighty designed His calendar to naturally include a 13th month, eliminating the need for artificial rules or adjustments like leap years or “non-days.” This design is self-adjusting, perfect, and beautiful in its simplicity.

Annual Sabbaths rely on the moon

The word “Month” on modern calendars is completely arbitrary.
But in Biblical times a “month” is one cycle of the moon.

2  This month [moon cycle] will be the beginning of months [moon cycles]; it will be for you the first of the months [moon cycles] of the year. 
~Exodus 12

But how was Moses to demarcate “the first month” in future years? How was he to know when spring began? Was he to base the New Year on vegetation (i.e. barley), or was he to look to the heavens? Genesis holds the answer:

14  And God said, “Let there be lights in the firmament of heaven to separate day from night, and let them be as signs and for appointed times, and for days and years, 
15  and they shall be as lights in the firmament of heaven to give light on the earth.” And it was so. 
~Genesis 1

There is not one single passage of scripture that states we are to observe the ripeness of Palestinian barley for establishing the New Year.

To make a biblical calendar, you have to use the rules found in the Bible. The Babylonian word “Abib” is superimposed over the Bible month delineations where the months, like days of the week, are NUMBERED… not given names.

A Sabbath is a sacred appointment between the Almighty and His people, we either met Him on the day of His choosing or we don’t. We can’t just decide for ourselves when the “appointed times” are. Those meetings are contingent on ordered periodic MOON CYCLES.

Here is a list of the “appointed times” spoken of in Genesis 1:14

19 He made the moon for appointed times; the sun knows its time for setting. 
~Psalm 104

Without question, the moon is used to determine “Months”

3  Blow the horn at new moon [Memorial of Trumpets], at full moon [Day of Atonement], for our feast day [Feast of Tabernacles], 
4  because it is a statute for Israel, an ordinance of the God of Jacob. 
~Psalms 81

Why the need for a 13th month?

Mankind lost the precise calendar after Joshua’s Long Day, and Ahaz Sundial that went backwards. But CHRISTIANS/ISRAEL did NOT lose the calendar… the Biblical rules for calendar making NEVER CHANGED! The problem is ancient man is highly dependant on crops, because they were an Agrarian society. But the most important reason for a 13th month is because that is what the Almighty has instituted.

19  He made the moon for appointed times; the sun knows its time for setting. 
~Psalm 104

Okay, so the great light of the night is for appointed times (Annual Sabbaths)… but why a 13th month?

Months play a vital role in God’s timepiece. Non-biblical calendars, including modern ones, struggle to create a system that maintains perfect time for both solar years and its months without drifting. When we try to divide solar years by “months”, that only complicates things.

There are 365.2422 days in a year, and 29.5 days in a lunar month. No calendar can calibrate those two chronologies perfectly… except ONE. The Biblical Calendar.

The Biblical Calendar has a yearly cycle with 13 months seven times in a 19 year cycle. But what makes it so beautiful is its simplicity. Nothing to do, nothing to calculate, nothing to figure in… its all automatic to keep perfect time. Men and their devices make it complicated, but in truth, its so simple even a shepherd boy can know exactly what time it is.

The 13th month adjusts the calendar to keep perfect time.

The first light of the New Moon after the Equinox is day one on the Sacred Calendar

The 13th Month in Ezekiel

The Prophet Ezekiel provides scriptural proof of a thirteenth month.  The Almighty told Ezekiel to act out a parable, revealing the fate of Jerusalem for rebelling against Heaven. 

In Ezekiel 1:1-2, Ezekiel received a vision on the fifth day of the fourth month in the fifth year of King Joakim’s captivity.

1  Now it came to pass in the thirtieth year, in the fourth month, on the fifth day of the month, that I was in the midst of the captivity by the river of Chobar; and the heavens were opened, and I saw visions of God. 
2  On the fifth day of the month; this was the fifth year of the captivity of king Joakim.
~Ezekiel 1

A few chapters later, in Ezekiel 3:15, the date of the 11th day of the fourth month in the same year is given.

15  Then I passed through the air and came into the captivity, and went round to them that dwelt by the river of Chobar who were there; and I sat there seven days, conversant in the midst of them. 
~Ezekiel 3

In Ezekiel 4:1-11, the Almighty tells Ezekiel to lay on his left side for 390 days and then on his right side for 40 days.  This is a total of 430 days.  The following passages describe Ezekiel’s obedience to this instruction. 

1  “Now, son of man, take for yourself a brick, and you must put it before you, and you must portray on it a city, Jerusalem. 
2  And you must build against it siege works, and you must build against it a bulwark, and you must heap against it a siege ramp, and you must set up against it camps and put against it a battering ram all around. 
3  And take for yourself a plate of iron, and you must place it as a wall of iron between you and the city, and you must set your face against it, and it must be under siege, and you must lay the siege against it; it is a sign for the house of Israel. 
4  And you, lie down on your left side, and you must put the guilt of the house of Israel on it. You will carry their guilt the number of days that you will lie on it. 
5  And I will give to you the years of their guilt according to the number of the days, three hundred and ninety days, and you must bear the guilt of the house of Israel. 
6  When you have completed these, then you must lie a second time on your right side; and you must bear the guilt of the house of Judah forty days, a day for each year, a day for each year I give it to you. 
7  And toward the siege of Jerusalem you must set your face and your bared arm; then you must prophesy against it. 
8  Now look! I will put on you cords, and you may not turn yourself from one side to your other side until you complete the days of your siege. 
9  “And you, take for yourself wheat and barley and beans and lentils and millet and spelt, and you must put them in one vessel, and you must make them for yourself into a food during the number of days that you are lying on your side; three hundred and ninety days you shall eat it. 
10  And your food that you will eat will be according to weight; twenty shekels for each day at fixed times you shall eat it. 
11  And an amount of water you shall drink, a sixth of a hin; at fixed times you shall drink it. 
~Ezekiel 4

The next specific date is given in Ezekiel 8:1

1  And then in the sixth year, in the sixth month, on the fifth day of the month [of King Joakins’ captivity], I was sitting in my house, and the elders of Judah were sitting before me. And the hand of the Lord Yahweh fell on me there, 
~Ezekiel 8

Ezekiel had accomplished the 430 days of lying on his side.  This is why, a year and two months later, he is sitting at home. 

One year=365 days
2 lunar months= 29 days + 30 days
“one year and two months” = 424 days 👈NOT ENOUGH DAYS

A full 430 days can only be accomplished on a lunar solar calendar during a year with an extra thirteenth month cycle.  If it were a strictly solar year of 365 days, there would not have been enough time for Ezekiel to finish lying on his side and be back home by the sixth month.

Just for giggles and kicks, here is what it would look like on any of the several Enochian calendars… Ezekiel would have DISOBEYED!

Using the Biblical instructions calendar (the same one Jesus used 600 years later), Ezekiel completed his assignment and had days to spare!

Objections to the 13th Month

Claim – The “exact” number of days God commanded were not literal. God just meant “a long time”

Answer -Thats funny, because the ACTUAL fulfillment of this Prophecy turned out to be exactly correct (390 & 40 days), to the year! Squirm and Hoop jump all you want. It is my firm belief the correct history is the one that lines up the the Biblical narrative. The LITERAL interpretation turns out to be EXACTLY correct to the historical facts!

https://writtenexposition.org/2024/02/21/four-symbolic-acts-in-ezekiel-41-54/
Going deeper, and its relevance to the present day:
https://www.bibleinsight.com/390days.html

Claim -Rev 22:1-2 says the Tree of Life has 12 leaves, one for each month… where is the 13th leaf?

Answer -The original calendar for earth was the Noah Calendar, it has exactly 12 months of 30 days each. The year was exactly 360 days long and divided by 12 perfectly. This is in line with the prophetic calendar of 360 days.
Rev 22 is speaking about the New Jerusalem, so it would appear, the Almighty will restore His Original Calendar that Noah used in the New Heavens & New Earth

Claim -The 13th month was infused by Pharisees.

Answer -Since Ezekiel used a 13th month Calendar in 600 BC, it would not be possible for it to come from Pharisees because they were not instituted until the second century BC during the Hasmonean Dynasty.

What’s more, the Temple Calendar (Biblical Calendar) was continuously in use for nearly 1500 years (except for about 70 years during the Babylonian captivity). There was only ONE calendar for the ancient Hebrews. It goes by a number of names eg. Hebrew Calendar, Sacred Calendar, Temple Calendar, Biblical Calendar

Claim -There are no cycles of 13 in scripture

Answer -In Matthew we see 3 sets of 13 genealogies to from Adam to Christ. Paul was the 13th Apostle. The Tetragrammaton (Name of God) is 2×13.

There are 13 tribes of Israel… yep, 13
1. Asher
2. Benjamin
3. Dan
4. Ephraim
5. Gad
6. Issachar
7. Judah
8. Levi
9. Manasseh
10. Naphtali
11. Reuben
12. Simeon
13. Zebulun

There were 13 land divisions of Israel. Levi was not given a portion of land, but Manassahs’ land was divided in two. Part on the East side and part on the West side, so we are back to 13 land divisions of Israel.

So if the argument is, God doesn’t use the number “13” of His numbering system for anything…. thats just flat out not true. The only “cycle” I can think of is His Sacred Calendar with the 13th month used seven times in a 19 year cycle.

Claim -1 Chronicles 27 lays out priestly monthly rotation schedule. But there is no order for duties for the 13th month.

Answer – The order was given by King David, not a command from God. David either failed to give specific duties for the 19 year cycle or the Prophet Jeremiah didn’t transcribe it. After all, Jeremiah was 400 years removed from the time of King David. Maybe we cut him a little slack.

This Priestly Rotation is presumed to be held even to the second temple period, of whom we KNOW has a 13th month, and it never was an issue. From King David to the Fall of Jerusalem in 70 AD… No problems, ever.

Claim – 1 Kings 4 speaks of individual cooks and a monthly schedule for each man through the year. There is no 13th month listed.

Answer – What if one of the cooks died? Would the calendar be lost? Perhaps this schedule was only for that year where there was not a 13th month. We have “leap years” today on the modern Gregorian Calendar… how many rosters’ do you know that mentions something special for a leap year? NONE! Again, this duty roster does not nullify the Biblical 13th month of Ezekiel

Claim – Ezekiel’s 13th month is not valid because Ezekiel wasn’t the only author of Ezekiel. Ez 1:2 is in first person, Ez 1:3 is written in third person.

Answer – Moses did not write about his own death, so is the Torah invalid? However the Almighty chose to preserve his word is His descision. Fact is MANY authors in the Bible switch back and forth from first to the third person, and this is seen in both the Old Testament and the New Testament. Writing in the third person was a common literary style in ancient times and does not necessarily imply that the author was not the subject or participant in the narrative. Here are some notable examples:

1. Moses:

Books: The Pentateuch (Genesis, Exodus, Leviticus, Numbers, Deuteronomy)

3 states, “Now the man Moses was very great in the land of Egypt, in the sight of Pharaoh’s servants and in the sight of the people.”
~Exodus 11

Deuteronomy 34: The chapter detailing Moses’ death and burial is written in the third person, suggesting that either it was added by a later editor or that Moses wrote it in the third person as a prophetic account.

2. Prophets:

3 says, “Then the Lord said to Isaiah, ‘Go out to meet Ahaz, you and Shear-Jashub your son.’”
~Isaiah 7

Jeremiah 20:1-2, where it states, “Now Pashhur the priest… heard Jeremiah prophesying these things.”

Daniel: The book of Daniel refers to Daniel in the third person in sections of the narrative, such as Daniel 1:6-7 and throughout much of the historical chapters.

3. Ezra:

Ezra 7:1 introduces him by saying, “Now after these things, in the reign of Artaxerxes king of Persia, Ezra the son of Seraiah…”

4. The New Testament

John frequently refers to himself as “the disciple whom Jesus loved,” as seen in John 13:23, John 19:26, and John 21:20. This is an instance of third-person narration even though John is the author of the book.

John 21:24 explicitly mentions, “This is the disciple who testifies to these things and who wrote them down.”

Matthew: The Gospel of Matthew refers to the author, Matthew, in the third person, such as Matthew 9:9, where it says, “As Jesus passed on from there, he saw a man named Matthew sitting at the tax office.”

Writing in the third person was not uncommon in ancient historical and religious texts. This style allowed authors to convey narratives and historical accounts in a way that could provide a sense of objectivity or denotation. While modern readers might see this as unusual, it was an accepted and effective narrative method in the literary context of the time.

Claim -Ezekiel 4:5 says 190 days in the Septuagint, should say 390 days.

Answer -That claim is TRUE! The Septuagint has a hoof print on that verse. Also, in v4 it introduces the number 150. Both of these numbers were introduced by the poison pen of the Scribes and Pharisees.

But the Almighty left us primary sources so that His children could know the TRUTH.

Lamsa Peshitta :
5 For I have given you two tasks of iniquities, according to the number of the days, three hundred and
ninety days; so shall you bear the iniquity of the house of Israel.
(Translation of the Syriac versions from the 2nd century)

Vulgate:
And I have laid upon thee the years of their iniquity, according to the number of the days three hundred and ninety days: and thou shalt bear the iniquity of the house of Israel.
(404 AD)

Justin Martyr :
“For I have laid upon thee the years of their iniquity according to the number of the days, three hundred and ninety days; so thou shalt bear the iniquity of the house of Israel.”
(Dialogue with Trypho, Chapter 112, (404 AD)

Origen:
“For I have assigned you the years of their iniquity, according to the number of the days, three hundred and ninety days; and you shall bear the iniquity of the house of Israel.”
(Homilies on Ezekiel, (593)

Those sources should be sufficient to prove the true rendering of Ezekiel 4:5

Claim -Ezekiel 8:1 “The fifth month” in the Septuagint, disagrees with the other MS

Answer -Yep, when the scribes lied in Chapter 4, they had to do it again to cover up their first lie. There is quite a bit of speculation of WHY they did that, and you are welcome to explore that discussion.
https://markhaughwout.com/Bible/Ezekiel_on_his_side.htm

But the fact remains, that we have other primary and secondary sources, of Bibles and quotes from early christian writers that we can have great assurance the true rendering of the verse.

“The sixth month” is the correct translation

Lamsa Peshitta:
AND it came to pass in the sixth year, in the sixth month, on the fifth day of the month, as I
was sitting in my house, and the elders of Judah were sitting before me, that the hand of the
LORD God fell there upon me.
(from 2nd century Syriac)

Claim -Ezekiel 1:1 is out of chronological order with 8:1, thus the timeline is false

Answer -There are two answers to this one. FIRSTLY, consider what these chapters are about. They are telling of a prophecy coming on Israel for their sin. One year for every year Ezekiel lays on his side. THIS HAPPENED exactly as prophesied.

Although secular history and archeology has some holes during this period, from a secular point of view, this prophecy happened. Non-believers get the timeline wrong. If you are making this mistake, you likely don’t understand the prophecy.

https://mundall.com/erik/ezekiel4.htm

SECONDLY, this difference between v1:1 and v8:1 is very simple, the verses don’t contradict but reflect different points of reference in Ezekiel’s prophetic and chronological record.

Ezekiel 1:1
“In the thirtieth year, in the fourth month, on the fifth day of the month, as I was among the exiles by the Chebar Canal…”

Interpretation: Scholars debate what “the thirtieth year” refers to. Some interpretations suggest it could relate to Ezekiel’s age, as he was from a priestly lineage, and the age of 30 was when priests began their temple service (Numbers 4:3). Others propose that this marks the 30th year of a significant event or calendar system, such as the Jubilee cycle. Still others say from the beginning of the reign of Nabopolassar, the father of Nebuchadnezzar, from which the Chaldeans began a new computation of time, as they had done from Nabonassar 123 years before.

https://www.christianity.com/bible/commentary/matthew-henry-complete/ezekiel/1

Ezekiel 8:1 “And it came to pass in the sixth year, in the sixth month, on the fifth day of the month…”

Interpretation: This verse clearly indicates the sixth year of King Jehoiachin’s captivity, a commonly used time marker in Ezekiel. This is about 5-6 years after Ezekiel was exiled, aligning with the timeframe of his prophecies during the Babylonian exile.

The apparent chronological difference between Ezekiel 1:1 and Ezekiel 8:1 can be explained through the context and different dating systems used in the text. There is absolutely no false timeline here.

Claim -there are no scriptural commands for a 13th month

Answer -Why would there be? There is nothing to calculate, nothing to install, nothing to do… its inserted at its proper time by Creation, the Almighty made it automatic.

Its simply just exists as Ezekiel clearly shows. It takes a Bible to make a Bible Calendar, useing “rules” outside of scripture is not a “Bible Calendar”.

World history of 13 month Lunisolar calendars

Almost all civilizations of the Ancients were based on the Metonic Cycle instituted at Creation week.

Babylonians:

Babylonians never had a calendar with 13 months based on the natural cycle… they inserted it artificially!
The ancient Hebrews never stole the Babylonian Calendar.

The Babylonian civilization (circa 2000 BC and later) used a lunisolar calendar with 12 lunar months of about 29.5 days each. To keep the calendar aligned with the solar year, they inserted an intercalary (leap) month approximately every three years. This method ensured that their calendar stayed in sync with agricultural and solar cycles.

https://en.wikipedia.org/wiki/Babylonian_calendar

Hebrews:

The ancient Hebrew calendar, used from biblical times through the Second Temple period, was lunisolar. It included the inspired automatic addition of a 13th month to maintain alignment with the seasons. The practice ensured that major feasts, such as Passover, occurred at precisely the right timing.

Who can argue that Jesus didn’t have the correct calendar?

Ancient Chinese:

The Chinese calendar is an ancient lunisolar system dating back to at least the Shang Dynasty (circa 1600–1046 BCE). It included intercalary months to prevent drift between the lunar and solar cycles. The insertion of a 13th month ensured that the Chinese New Year and other key festivals stayed within the proper season.

There is great evidence that the ancient Chinese had a strong Christian community. The “Wise Men from the east” who visited Jesus at his birth were chinese. There is also evidence built directly into their language.

https://chinesehsc.org/chinese_calenders.shtml

Greeks:

The Ancient Greeks, particularly during the era of Meton of Athens (circa 432 BCE), developed the Metonic cycle, which synchronized the lunar and solar years over a 19-year cycle. The system included the insertion of 7 intercalary months within a 19 year cycle to keep their calendar in sync with the solar year.

Persians (Achaemenid Empire):

The Achaemenid Persians (circa 550–330 BCE) adopted elements of the lunisolar calendar system. Though their primary calendar eventually became more solar-based, there are indications that earlier practices included intercalations to reconcile lunar and solar cycles.

Romans (Pre-Julian Calendar):

The early Roman calendar, before Julius Caesar’s reforms in 45 BCE, was a lunisolar system that sometimes included an intercalary month called Mercedonius. Although it was not consistently applied, it was meant to keep the calendar in sync with the seasons. The process, however, was prone to manipulation and irregularities.

Mayan Civilization:

The Maya used complex calendar systems, including the Haab’, a solar calendar of 365 days, combined with the Tzolk’in, a 260-day ritual calendar. While primarily not a lunisolar system, the Maya Long Count and calendar rounds sometimes included calculations for synchronization with lunar cycles. This led to adjustments that could be seen as similar in concept to intercalary months.

Rabbinical (Greek Calendar):

Post-exilic Pharisaic practices during the Hellenistic period used a lunisolar system influenced by the Sacred Calendar practices but added their own variations. This system included the 13th month and was standardized.

Hindu Calendars:

Ancient Hindu calendars have been lunisolar for millennia, with systems incorporating a leap month known as Adhik Maas. This additional month is inserted roughly every 2.5 to 3 years to maintain alignment with the solar year. The use of lunisolar calendars dates back to the Vedic period (circa 1500–500 BCE).

Ancient Egyptians (Lunar Influence):

While the Ancient Egyptian calendar was predominantly solar, their earlier timekeeping methods included tracking lunar cycles. The integration of lunar and solar observations suggests that they may have initially adapted lunisolar practices of the Hebrews (Joseph and family) before transitioning to a purely solar calendar.

Armenians:

The Armenian calendar had lunar influences, and while primarily solar by the Middle Ages, earlier iterations may have incorporated adjustments similar to the Sacred Biblical Calendar systems they encountered. These intercalations helped maintain seasonal consistency.

Ancient Japanese Calendar:

Before adopting the Chinese calendar fully, early Japanese calendars combined lunar and solar elements. The lunar months were periodically adjusted with a 13th month to align with the solar year, a practice that continued under Chinese influence.

Korean Calendar:

The ancient Korean calendar, heavily influenced by the Chinese lunisolar system, included intercalary months to reconcile lunar and solar discrepancies. This practice ensured that traditional festivals remained in their respective seasons.

Phoenicians:

The Phoenician calendar was lunisolar, likely influenced by the Sacred Calendar through Babylonian practices due to their extensive trade and interactions. They included the 13th month as it occurred to keep their calendar aligned with the solar year, facilitating navigation and agriculture.

Assyrians:

The Assyrian Empire (circa 2500–605 BCE) followed practices influenced by the Sacred Calendar through the Babylonian lunisolar calendar. This included adding an intercalary month to align with solar cycles, essential for their religious festivals and agricultural cycles.

Ancient Sumerians:

The Sumerians, among the earliest known civilizations (circa 3500–2000 BCE), had a calendar system that included the intercalary 13th month to harmonize the lunar and solar years. Although documentation is scarce, their calendars influenced later Babylonian timekeeping methods.

Hittites:

The Hittites (circa 1600–1178 BCE) in Anatolia used a lunisolar calendar that included the 13th month. This was essential for scheduling their seasonal festivals and aligning religious observances with solar patterns.

Ancient Syrians:

The calendar system of ancient Syria included lunar months and solar adjustments, similar to those in Babylon. The influence of neighboring Mesopotamian cultures likely contributed to their use of a lunisolar calendar, which required periodic additions of extra months to align with the solar year.

Elamites:

The Elamite civilization (circa 2700–539 BCE), located in present-day southwestern Iran, had cultural and calendar similarities with the Mesopotamians, incorporating lunisolar adjustments of the 13th month for religious observances and agriculture.

Pre-Islamic Arabian Tribes:

Some ancient Arabian tribes used a lunisolar calendar to track time for agricultural and trading purposes before the widespread use of a purely lunar Islamic calendar. This system included the 13th month to synchronize the lunar months with the solar year, helping manage trade routes and seasonal activities.

Ancient Ethiopians:

In ancient Ethiopia, the early calendar system combined solar and lunar elements. Although more closely associated with later periods, there is evidence that the roots of their timekeeping involved periodic intercalary adjustments of a 13th month similar to their neighbors, influenced by Egyptian and Babylonian practices.

Celtic Tribes:

While detailed records are limited, Celtic tribes in pre-Roman Europe are believed to have used lunisolar systems to track the seasons and significant religious events. The Coligny calendar, dating to the 1st century BCE, suggests that a system of the intercalary 13th month was already in use, which likely developed over centuries prior.

Ancient Canaanites:

The Canaanites likely used a calendar influenced by their Mesopotamian and Egyptian neighbors. This calendar may have included intercalary 13th month for aligning their religious festivals with the solar year.

Minoan Civilization:

The Minoans of ancient Crete (circa 3000–1450 BCE) might have used a form of lunisolar calendar, based on archaeological finds that suggest a sophisticated understanding of timekeeping for religious and agricultural purposes.

Pre-Columbian Native American Tribes:

Most pre-Columbian calendars, of Native American tribes were lunisolar that accounted for the 13th month. They were most likely part of a tribe of the Northern 10 tribes of Israel. They had the 10 Commandments in stone, the called their God “Yahuwah”, much Hebraic idioms in their language. So, it only makes sense that they had the Sacred Calendar.

https://kingdomtruther.com/thats-what-the-old-ones-say

Harrapan/Indus Valley Civilization:

The Indus Valley Civilization (circa 3300–1300 BCE) had a complex society that included advanced timekeeping, possibly influenced by lunar and solar cycles. While direct evidence of a lunisolar calendar with the 13th month is scarce, their sophisticated planning and agricultural practices imply that some form of synchronized calendar was in use.

Zoroastrian:

Early Zoroastrian practices in ancient Persia might have utilized a lunisolar system before transitioning to a more purely solar calendar in later periods. This is inferred from interactions with Babylonian and earlier Assyrian cultures.