The Sabbath Was Changed To SUNday
This Falling Away of 2 Thessalonians 2 study proves that Sunday is not the Biblical Sabbath day, and neither is Saturday.
It will show that the Seventh Day Adventists, the Hebrew Roots Movement people, most Torah Christians and anyone else who teaches that Saturday is the Sabbath; are wrong.
The reason that Saturday and Sunday are wrong is because they’re based on the Solar Roman Gregorian calendar. But the Biblical calendar is luni-solar, where the Sun defines the years and day, and the moon defines the months and weekly Sabbaths.
Saturday Sabbath followers correctly point out that Emperor Constantine changed the Sabbath to Sunday, in the 4th century; and that the Roman Catholic Church claims the authority to dictate a Sunday Lord’s Day.
But what they fail to understand is that Constantine did not change it from Saturday to Sunday, as the Jews and Christians did not observe it on Saturday.
What he did was forbid Jews and the Early Church from following the luni-solar calendar, which resets the calendar each month based on the 29 1/2 day lunar cycle, which caused the day that the Sabbath was observed on to change every month.
Constantine forced them to observe a Solar-based calendar, which featured a repeating cycle of 7 days; or be subject to death.
In 358 A.D., Sanhedrin patriarch Hillell II compromised with Rome when he provided a mathematically-based calendar that would harmonize with the Roman Sun-based calendar, while appearing to still be based on the luni-solar Biblical roots.
In order to reduce persecution by Rome, the Jews exchanged Biblical lunar Sabbaths for the popularized Roman unbroken-cycle-of seven day weeks. This causes their Sabbaths to be out of sync with the New Moons, and with the holy appointed Feast Days.
Since then, Jewish leaders have developed “Rules of Postponement” to make sure that while following the Roman calendar, that certain Holy Days are not adjacent to the Saturday Sabbath.
But their “Rules of Postponement” are not Biblical, which confirms that the Rabbis are not using the Scriptural Calendar for the seventh day Sabbath!
To prove that Saturday cannot be the weekly Sabbath, one simply has to read about Aviv 10, when the Passover Lamb was to be purchased; Aviv 14 which is a preparation day for the first day of Unleavened Bread, and Aviv 16, on which the barley could be harvested.
All of those are commanded work days, so they cannot possibly fall on a Sabbath. But on the Roman Gregorian calendar they do fall on Saturday every few years, so it invalidates the premise.
The same problem happens on the Enoch calendar, on which the Sabbath day is assigned to the same day of the Roman calendar all year. This year it is on Wednesday.
But this causes violations of Torah, as this year Passover fell on the Sabbath Day.
The 14th of Abib, Passover, is a commanded work day. It is a preparation day for the High Sabbath of the Feast of Unleavened Bread. It is the day on which the Israelites would have brought in their Passover lamb to be slain.
So Passover, a commanded work day, cannot fall on a Sabbath day; which invalidates the Enoch calendar explanation.
People who observe a Saturday Sabbath say that the 6 work day / 1 Sabbath Day cycle has repeated continuously since it started in Genesis; but that simply is not true.
The 6 work day / 1 sabbath day cycle is interrupted as their High Sabbaths of Unleavened Bread and Tabernacles fall on work days. So in one week there are two Sabbath days and only five work days; and the 6/1 cycle in interrupted.
Only on a lunisolar calendar are the High Feast Days on the weekly Sabbath Day, thus the name, High Sabbath.
The Biblical Calendar: The Lunar-Solar Calendar of Creation
This is the only calendar that uses the monthly cycle of the moon and the yearly cycle of the Sun, to keep that Holy Feast Days in their proper season.
The luni-solar calendar can be used by anyone to determine the new month and the 7th day Sabbaths.
Note: The above video, and other resources on this page, are from World’s Last Chance. Sadly WLC now embraces the Flat Earth Deception, which I expose on my website. For now I’m keeping these resources on the study, as they provide great information; but I will look for other sources, as the flat earth deception hurts their (and my) credibility.
A Biblical month has a New Moon Day, work days and weekly Sabbath day.
It is impossible for the Creator’s weeks to have cycled without end, since creation, for the mere fact that there are three kinds of days each month and not just two.
Ezekiel 46:1 tells us that there are working days, weekly sabbath days and the New Moon day.
Thus says the Lord GOD: “The gateway of the inner court that faces toward the east shall be shut the six working days; but on the Sabbath it shall be opened, and on the day of the New Moon it shall be opened.
These verses also define sabbath days and new moon days as separate days:
Behold, I build an house to the name of the LORD my God, to dedicate it to him, and to burn before him sweet incense, and for the continual shewbread, and for the burnt offerings morning and evening, on the sabbaths, and on the new moons, and on the solemn feasts of the LORD our God. This is an ordinance for ever to Israel. 2 Chronicles 2:4
Even after a certain rate every day, offering according to the commandment of Moses, on the sabbaths, and on the new moons, and on the solemn feasts, three times in the year, even in the feast of unleavened bread, and in the feast of weeks, and in the feast of tabernacles. 2 Chronicles 8:13
He appointed also the king’s portion of his substance for the burnt offerings, to wit, for the morning and evening burnt offerings, and the burnt offerings for the sabbaths, and for the new moons, and for the set feasts, as it is written in the law of the LORD. 2 Chronicles 31:3
For the shewbread, and for the continual meat offering, and for the continual burnt offering, of the sabbaths, of the new moons, for the set feasts, and for the holy things, and for the sin offerings to make an atonement for Israel, and for all the work of the house of our God. Nehemiah 10:33
Saying, When will the new moon be gone, that we may sell corn? and the sabbath, that we may set forth wheat, making the ephah small, and the shekel great, and falsifying the balances by deceit? Amos 8:5
The Hebrew word for ‘moon’ is chodesh, which means the new moon; by implication, a new month.
This invalidates the concept of a continual 6 work day / 1 Sabbath day cycle.
The first day of the month would be the New Moon Day, which starts at the dawn after the moon conjunction (dark moon).
Then there would be a cycle of 6 days of work, followed by a weekly Sabbath rest, which would occur on the 8th, 15th, 22nd and 29th of each month.
Note: A Biblical day starts at dawn, which makes perfect sense. Day and Night are two different entities. Day starts at dawn and ends at dusk, from even unto even.
“And Elohim made two great lights; the greater light to rule the day, and the lesser light to rule the night: he made the stars also.” Genesis 1:16
The Roman calendar day starts at midnight, when it is completely dark, which does not line up with the Bible. The Jews traditional day starts when the Sun goes down, which again does not line up with the Bible.
One can look at the record of Messiah’s crucifixion to see when a day starts. Messiah was impaled on the cross at 9am, three hours after the day started. He died six hours later, at the 9th hour, at 3 pm.
“And it was the third hour, and they impaled Him.” Mark 15:25
“And when the sixth hour came, darkness came over all the land until the ninth hour.” Mark 15:33
“And at the ninth hour Yahusha cried out with a loud voice, saying, “Ěli, Ěli, lamah sheḇaqtani?” which is translated, “My Ěl, My Ěl, why have You forsaken Me?” And Yahusha cried out with a loud voice, and breathed His last.” Mark 15:34, 37
Mark 15:42-43 invalidates that the day starts at sundown, for they took Messiah’s body AFTER the evening began. If the Sabbath started at sundown, then they were working on the Sabbath. But the text states that it was still the preparation day for the Sabbath, the 14th, Passover.
“And now when the even was come, because it was the preparation, that is, the day before the sabbath, Joseph of Arimathaea, an honourable counsellor, which also waited for the kingdom of God, came, and went in boldly unto Pilate, and craved the body of Jesus.”
These videos provide many Scriptural proofs that a day starts in the morning.
WHEN DOES A DAY START – MORNING OR EVENING? PART 2
In the middle of the month the full moon would appear.
The full moon would be shining bright during the major Feast Days of Unleavened Bread and Tabernacles, which occur on the 15th of the 1st and 7th month.
Because the Holy Feast Days of Unleavened Bread and Tabernacles occur on the 15th, which is a Sabbath Day, they are called a “High Sabbath“.
John 19:31 tells us that the day after Passover is the Sabbath, meaning it is the 7th day of the week. THEN it adds that it is a high Sabbath, meaning it is also a Feast Day.
Therefore, since it was the Preparation Day, that the bodies should not remain on the stake on the Sabbath – for that Sabbath was a high one – the Yehuḏim asked Pilate to have their legs broken, and that they be taken away. John 19:31
This proves that the Feast of Unleavened Bread, which Scripture declares is on the 15th of the 1st Biblical month, is always on the 7th day Sabbath. This proves that the weekly Sabbaths are always on the 8th, 15th, 22nd and 29th of each luni-solar month.
Since the calendar resets every month based on the lunar cycle, the first day (new moon day) of the next month can land on any Gregorian calendar day, and the Sabbaths which fall on the 8th, 15th, 22nd and 29th, would also fall on that same day.
For example, if the first day of the new Biblical month fell on Wednesday of the Roman calendar, then the weekly Sabbaths would fall on Wednesday as well, as they occur every 7th day.
Below is how the month calendar with the weekly Sabbaths would look for the 1st month on the year, which occurs in Spring and includes the Holy Feast Days of Passover and Unleavened Bread.
As you can see, the Holy Feast Day of Unleavened Bread falls on the 15th, on the Sabbath Day, making it a High Sabbath.
Leviticus 23:39 the Father commanded us to start the Feast of Tabernacles on the 15th day of the 7th month, which is a sabbath, making it a High Sabbath. Then on the eight day of the Feast, on the 22nd, He said it is also a Sabbath, proving the pattern of 8th, 15th, 22nd and 29th.
“Also in the fifteenth day of the seventh month, when ye have gathered in the fruit of the land, ye shall keep a feast unto the LORD seven days: on the first day shall be a sabbath, and on the eighth day shall be a sabbath.”
Instead of debating verses about the Sabbath, which causes most people’s minds to blur, let’s focus on clear examples in scripture, which reveal the truth.
Here are many Scriptural proofs which show that the weekly Sabbaths occur on the 8th, 15th, 22nd and 29th of each luni-solar month:
Scripture proves that the 15th of the first luni-solar month is a Sabbath Day.
In the 1st month (Abib) of the Biblical calendar, the Passover falls on the 14th day, and the High Sabbath of the Feast of Unleavened Bread falls on the 15th.
“In the fourteenth day of the first month at even is the LORD’S passover. And on the fifteenth day of the same month is the feast of unleavened bread unto the LORD: seven days ye must eat unleavened bread. In the first day ye shall have an holy convocation: ye shall do no servile work therein.” Lev. 23:5-7
The Feast of Firstfruits is celebrated on the day after the 1st day of Unleavened Bread, which is the weekly Sabbath, again confirming that it occurs on the 15th.
“When ye be come into the land which I give unto you, and shall reap the harvest thereof, then ye shall bring a sheaf of the firstfruits of your harvest unto the priest: And he shall wave the sheaf before the LORD, to be accepted for you: on the morrow after the sabbath the priest shall wave it.” Lev. 23:10-11
Scripture proves that 40 years after the Israelites left Egypt, the Feast of Unleavened Bread High Sabbath continued to be on the 15th.
The cycle of a New Moon day, six work days and a weekly Sabbath day, continued for 40 years. At the end of the 40 years, after the high day Sabbath of the Feast of Unleavened Bread, the manna ceased on the next day, a work day, on which they would have normally gathered it; and they entered into Canaan.
“And the children of Israel encamped in Gilgal, and kept the passover on the fourteenth day of the month at even in the plains of Jericho. And they did eat of the old corn of the land on the morrow after the passover, unleavened cakes, and parched corn in the selfsame day. And the manna ceased on the morrow after they had eaten of the old corn of the land; neither had the children of Israel manna any more; but they did eat of the fruit of the land of Canaan that year.” Joshua 5:10-12
Some argue that the Father provided manna to the Israelites for six days and had them gather a double portion the day before the Sabbath.
But they had herds of animals, flour and oils to prepare bread, etc., so they did not just survive on manna everyday for 40 years.
The Father used the manna to teach them the monthly cycles and weekly Sabbaths, and to test them.
The monthly cycle of the stars and moon declare the glory of our Creator. When you follow the Roman solar-based calendar, you are out of sync with the Father’s creation.
By observing the months and weekly Sabbaths around the lunar cycle, this causes His followers to be in synchronicity with the heavenly realms of worship.
The dedication of the priesthood of Aaron and his sons was on the 8th day Sabbath.
During the first month of the second year since their departure from Egypt in which Passover was to be kept, Aaron and his sons were inducted into the Priesthood and sanctified for seven days beginning on New Moon Day (Exodus 40:2,17).
On the eighth day, which was the 8th day of the lunar month, there was an assembly of the congregation for worship, identifying the 7th day Sabbath.
Solomon honored the 22nd day Sabbath.
Solomon faithfully kept the Feast of Tabernacles for seven days, starting on the 15th of the month, a High Sabbath. As commanded, they made a solemn assembly on the 22nd, the next weekly Sabbath.
He then sent the people away on the eighth day, the 23rd of the month, which was the 1st day of the week. So we have a confirmation of the 15th being the High Sabbath and the 22nd being the next Sabbath. (2 Chronicles 7:8-10).
King Hezekiah honored the 8th day Sabbath.
The people began to sanctify on New Moon day of the first month, then on the 8th of the month they went to the temple.
On the 16th of the month, they “made an end,” which was the first day of the work week (2 Chronicles 29:17). Here again the Sabbaths are fixed to the 8th, 15th, 22nd and 29th lunar calendar dates.
After the famous Battle of Jericho, they rested on the 8th day, the weekly Sabbath.
The Israelites marched around Jericho for seven days, in offensive battle readiness, and attacked the city on the seventh day.
If the continually repeating six work days / 1 Sabbath day cycle were true, then they would have been walking on a Sabbath day, which is a clear violation of the Father’s commands.
This is explained by the fact that the first day was the New Moon Day, the first day of the month. They marched for six more days, and then they rested on the 8th, the weekly Sabbath.
The “Book of Jasher”, which is not in the Bible but is historically useful, even says the march started on the New Moon Day.
Our Messiah healed the blind man on the 22nd day, on the weekly Sabbath.
The last day of the Feast of Tabernacles is fixed to the 21st day of the 7th month of Ethanim (Leviticus 23:34, 36, 39-41; Numbers 29:12; Deuteronomy 16:13-15; Nehemiah 8:13-18; Ezekiel 45:21-25).
Our Messiah, Yahushua, attended the Feast of Tabernacles (John 7:10).
On the last day of the feast, the 21st of the 7th month, Messiah stood and spoke (John 7:37; compare with Leviticus 23:33-36).
Our Messiah spent that night of the 21st on the Mount of Olives (John 8:1).
The next morning, the 22nd of the 7th month, our Messiah returned to the temple because it was the 7th day Sabbath (John 8:2; compare with Leviticus 23:33-36 ). At the temple the Messiah healed a blind man (John 9:6).
The healing of the blind man caused great anger among the Priests, for it was the 7th day Sabbath and they believed it was sin to perform such a miracle upon the Sabbath day (John 9:14).
This places the weekly 7th day Sabbaths in our Messiah’s time on the 8th, 15th, 22nd, and 29th of the month yet again.
Christ’s death on Passover proves that the Sabbath is not Saturday or Sunday
Our Messiah died in 31 A.D. on Passover. The New Moon Day of the 1st month of the Biblical calendar which occurred in 31 A.D., was on 3/13.
The Passover occurs on the 14th of the month, which means that Messiah died on 3/26, a Monday.
As you can see, there is no way that Messiah rose 3 days later on a Saturday or Sunday.
And the point is mute, as the Roman Calendar in 31 A.D. was an 8-day calendar, which did not even have a day named Sunday.
The first day of the Feast of Unleavened Bread, a High Sabbath, occurred on the 7th day of the week, which was 3/27 A.D.
And He rose again the next day, on the Feast of Firstfruits, which was the 1st day of the next week.
This invalidates the Messiah rose on Saturday or Sunday, which is used by people to justify that day as the Sabbath.
The High Sabbath Feast Days in both Spring and Fall, occur on the 15th.
Every time in Scripture where the Feast of Unleavened Bread or the Feast of Tabernacles is mentioned, they are always fixed to a 7th day Sabbath. There is no mention in Scripture of either of these set-apart feasts commencing on a day other than the 7th day Sabbath.
The beginning lunar calendar date for both was always the 15th counting from the New Moon. Therefore, this fixed all the other Sabbaths for the first and seventh month on the 8th, 22nd , and 29th each year. (Leviticus 23:5, 6, 34, 35; Numbers 29:12 -39).
According to Leviticus 23 and the Sanctuary luni-solar time model, every year the Feast of Unleavened Bread begins on the 15th of the First Month of Abib, which is always fixed to a 7th day Sabbath.
Six months later, the first day of Feast of Tabernacles also falls on the 15th, which is fixed to a 7th day Sabbath, as well. This seven-day feast is followed eight days later by a “sacred convocation” (7th day Sabbath) on the 22nd, each and every single year.
These two feast days, according to Scripture consistently commence on the 7th day Sabbath, which are identified as the 15th of their respective months, a full six months apart exactly.
Using the Biblical criteria above it is impossible to place both feasts six months apart and have them both commence on the 15th of the Roman Gregorian calendar month and be on a Saturday.
If per chance one year it happens to successfully work out, it cannot occur two years in a row and definitely not every year, as is required by Scripture.
The problem lies within the Gregorian calendar’s promotion of the unbroken-cycle-of-successive-weeks. Over and over again Scripture demonstrates that it has never utilized an unbroken continuous weekly cycle. (Numbers 29:12 – 39; Leviticus 23:5, 6, 34, 35).
Here’s a link to a Bible study that provides more examples of the Sabbaths falling on the 8th, 15th, 22nd and 29nd; proving the lunisolar calendar http://www.nccg.org/642Art-SabbathDays.html
Logic proof that you cannot determine the correct days and months using man-made calendar concepts.
Yahuah’s calendar works no matter where you are on the planet.
The brilliance of the lunar-based monthly calendar is that no matter where you are on Earth, you can determine the start of the new month, and the weekly Sabbaths, based on the lunar cycle.
Using man’s creation of the International Date Line just adds confusion to this.
It can be Friday for a person on one side of the date line and Saturday for a person on the other side; yet they may only be a few miles apart, and are looking up at the moon or sun, rising and setting, at the same time.
So for one person it would be Friday and the other it would be the Saturday Sabbath.
The Roman calendar is not compatible with the commands of Scripture regarding when to celebrate the Sabbaths and Holy Feast Days.
The Julian calendar, which was established in 45 B.C. and was in existence until 37 A.D., had an 8-day week, where the days of the week were assigned letters: A through H.
So the 6/1 pattern simply could have repeated in that 8-day per week calendar. And to claim that the Jews kept track is dubious at best.
Sunday cannot be the day that our Messiah rose again, because there was no Sunday.
Later in the first century, when Mithraism became a popular religious cult in Rome, it brought with it a 7-day calendar which had days that were names after planetary gods.
The week started on Saturn day (Saturday), Dies Solis (Sunday) was the second day of the week, Luna (Monday) was the third day, and dies Veneris, Venus Day (Friday), was the seventh day of the week.
Again, this does not reconcile with 6 days of work and 1 day of rest on the Saturday Sabbath.
Jews wrongly proclaim that the New Year starts when they sight the crescent moon in Jerusalem.
The modern Hebrew word for “New Moon” is chodesh (H2320), which is also translated as “month.” Chodesh appears in Scripture more than 270 times, yet it is not used even once to denote seeing something (i.e. the visible moon, the crescent, etc.). Rather, the Hebrew word signifying the physical, observable moon is yerach (H3391, H3393, & H3394). Yerach is translated 28 times as “moon” and 13 times as “month,” but is never used to signify the New Moon/month.
There is a Hebrew word for “crescent” – śaharōnîm (H7720). However, it is used exclusively in connection to heathen idolatry (Judges 8:21 & 26; Isaiah 3:18), and is never associated with the “New Moon” or even the “month.”
The New Moon which determines the start of the new Biblical year in 2016, happens on 3/09/16, the day after the dark conjunction.
It’s clear what defines a ‘New Moon’, the dark conjunction when there is no light on the moon, and it starts to wax towards a full moon.
Elohim setup the moon to keep His people in synchronicity with the Sabbaths.
No matter where they at on earth, they can observe the moon and know where they are at on the calendar.
The first quarter 1/2 moon falls near the 1st Sabbath on the 8th day; the full moon falls near the Sabbath on the 15th day; and the last quarter 1/2 moon falls near the 3rd Sabbath on the 22nd day.
These videos help you see how the objections to the lunisolar Sabbath are overcome with Scripture.
In Defense of the Lunar Sabbath | Part 1
In Defense of the Lunar Sabbath | Part 2
In Defense of the Lunar Sabbath | Part 3
Here is a link to an online tool which gives you a Biblical calendar, with the Sabbath Days and Feast Days, based on where you live:
Here is a PDF of the World Last Chance calendar until 2024 (based on Colorado time zone). You can create your own on the WLC calendar by printing 99 months. The only real difference for people in North America is the dawn and dust times of the Sabbaths and Feast days, which you can adjust from MST.
One objection people have to the lunisolar calendar is that a 13th month has to be added to keep the feasts in sync with the seasons.
They cite that no Bible passage declares the need to add a 13th month.
What they are not understanding is that when the instructions were given to the Israelites, the Sun’s yearly orbit took 360 days, and the moon’s orbit took 30 days.
They were in perfect sync, so there was no need for a 13th month to keep the feasts in their proper season.
7.5 days after the dark conjunction, the first quarter moon was visible on the 8th day Sabbath
The full moon was visible on the 15th day Sabbath
22.5 days after the dark conjunction, the last quarter moon was visible on the 22nd day Sabbath
Scripture describes this time, when the sun was moved out of place, in 2 Kings 20:9-11
And Yeshayahu said, “This is the sign for you from יהוה, that יהוה does the word which He has spoken: shall the shadow go forward ten degrees or go backward ten degrees?”
And Ḥizqiyahu said, “It would be easy for the shadow to go down ten degrees; no, but let the shadow go backward ten degrees.”
And Yeshayahu the prophet cried out to יהוה, and He brought the shadow ten degrees backward, by which it had gone down on the sundial of Aḥaz.
Ancient Chinese astronomers recorded the sun rose and set twice in one day in 705 B.C.
Dr. Immanuel Velikovsky in his book, Worlds in Collision, shows evidence that these 30 cultures worldwide all record a period of upheaval lasting about 50 years when the days of the month and days of the year were in flux before it settled down to what we have now–a year of ~365 1/4 days and a month of ~29 1/2 days.
The moon’s orbit around the earth was also changed slightly so that the regular 30 day orbit came to have a 29 1/2 day cycle.
Dale W. Wong in his 2006 book, The Ancient 360 Day Year: What It Was And How It Changed , laid out a simpler thesis than Velikovsky’s near collision scenario. Mr. Wong calculated the year when King Hezekiah in Judah was healed, and God gave a sign by moving the sun back 10 degrees on the sundial.
Dale Wong calculated the year of Hezekiah’s sundial sign to be 713 BC; and he posits that God actually moved the orbits of the earth and moon to accomplish this sign of moving 10 degrees/steps backward on the sundial.
Dr. Velikovsky and Dale Wong both show that there were 30 cultures around the world that used the 360 day year with 30 day months, before ~713 BC.
The ancient Vedas of India showed a 360 day year in the Brahmanas and they record that the moon waxed for 15 days and waned for 15 days in a month. The Brahmanas also state that the sun moved north 180 days and moved south 180 days in a year.
In a later period the Vedas record that the year was reformed to 365 1/4 days. In ancient Persia, the calendar had 360 days; later, it was reformed to add 5 Gatha days to the year length. The Sumerians had a 360 day year with months of 30 days, and the Babylonians adopted that Sumerian calendar. At the beginning of the 7th century BC, Babylon added 5 days to the year length. In ancient Assyria, the clay tablets from the royal library in Nineveh showed a 360 day year with 30 day months, and that the spring equinox always fell on Nisan 15. In Ancient Egypt, the Canopus Decree and Ebers papyrus calendar had 30 day months and a 360 day year. The year change occurred in the 8th or 7th century BC according to Plutarch and the Book of Sothis, with 5 epagomena days added to the year length. Rome at the time of Romulus had 360 day years. The Mayans of Mexico and Incas of Peru in Central and South America had a 360 day year calendar; later they added 5 1/4 days to the calendar. Other cultures like China and Polynesia had 360 day calendars that they amended by adding 5 days to the year–China called their added 5 1/4 days, Khe-ying days. The 360 degree circle and 360 degree compass in use all over the world is a remnant of the year length prior to the change, when the year length was exactly 360 days.
Numis Popilius the second king of Rome added 5 days per year to the 360 day calendar.
King Hezekiah at the same time, reorganized the calendar. He added a month each leap year, on a cycle of every 7 in 19 years, to make up the adjustment. This is exactly what the WLC calendar does.
So we can see why a 13th month is now necessary 7 out 19 years, to keep the feast days in sync with the seasons.
Here is a list of more detailed studies:
Messianic Evangelicals Creation or Lunar-Solar Calendar http://www.nccg.org/creation_calendar.html
New Moons & Manna | The Pattern in the Wilderness
Biblical Calendation: Reckoning the New Year
New Moon Day: The Dawn After Conjunction
Calculating the Conjunction: No Computer? No Problem!
Lunar sabbaths proven by proper Pentecost calculation
Future Lunar-Solar Conjunction Dates (2013-2023)
Constantine I & Hillel II: Two Men Who Deceived the Whole World
The New Moon In Scripture Is A Dark Moon PDF
WHEN DOES A DAY START – MORNING OR EVENING? PART 3
WHEN DOES A DAY START – MORNING OR EVENING? PART 4
WHEN DOES A DAY START – MORNING OR EVENING? PART 5
Next Study: 3 Days And 3 Nights Deception