The book of Numbers tries to provide the information of what happened from second year and then jumps to the last few years. In summary, book of Numbers tries to present what happened after the first year of Exodus, or as a continuation of the book of Exodus to the reader.
Before Inheriting the Land (before 1428 BC)
Num 36:13 These are the commandments and the judgments which the LORD commanded the children of Israel by the hand of Moses in the plains of Moab by the Jordan, across from Jericho.
The book of Numbers itself says it is before inheriting the promised land. This suggests that the book must be written around 1428 BC. However, it is important that we take this information with a grain of salt taking into account of all the other internal Scriptures evidences from this book.
After Inheriting the Land (after 1428 BC)
Exod 34:22 “And you shall observe the Feast of Weeks, of the firstfruits of wheat harvest, and the Feast of Ingathering at the year’s end.
Num 29:12 ‘On the fifteenth day of the seventh month you shall have a holy convocation. You shall do no customary work, and you shall keep a feast to the LORD seven days.
We discussed in How did year end became seventh month? how the book of Exodus is as old as the Exodus itself by proving the references to Egyptian Calendar. The feast of Ingathering or Tabernacles occurs on 7th month in the calendar given by God based on seasons in ancient Israel. However, the feast of Ingathering occurs at year end in Egyptian calendar based on the seasonal cycles of river Nile. This proved to us that the book of Exodus was written around 1468 BC. In the book of Numbers, we can see that the name of the feast was not mentioned either as Ingathering or Tabernacles but the reference for “a feast” was provided on the 7th month. This suggests, the book of Numbers was written after the children of Israel inherited the land, which must be after 1428 BC.
After Hormah was named (after 1403 BC)
Num 21:3-4 And the LORD listened to the voice of Israel and delivered up the Canaanites, and they utterly destroyed them and their cities. So the name of that place was called Hormah. They traveled from Mount Hor by the way to the Red Sea, to go around the land of Edom. The soul of the people was very discouraged because of the journey.
Judg 1:17 And Judah went with his brother Simeon, and they attacked the Canaanites who inhabited Zephath, and utterly destroyed it. So the name of the city was called Hormah.
The event mentioned here was a later recollection of the same event mentioned in the book of Judges 1:17 by later scribes who wrote it and/or the redactor who placed it there. It is also worth noting that the first 3 verses are from Yahwist source, the rest of the continuation from the book of Numbers are from Elohist source and the same event in Num 33:40 was from the redactor. Hormah is well within the promised land, between Beersheba and Hebron and Mount Hor is at the border of Edom as per Num 20:23. Hence, it is simply not possible to go from Mt Hor well within the promised land to capture Hormah and then return. The references from the book of Numbers are a later recollection and redactor’s effort in retelling the story with additional information on what happened in the book of Numbers.
Hormah was named after Joshua died. Joshua lived 110 years and was 85 when he came into the promised land. This means, Hormah was named after 1403 BC.
After the term ‘prophet ‘ instead of ‘seer’ (After 1095 BC)
Num 11:29 Then Moses said to him, “Are you zealous for my sake? Oh, that all the LORD’s people were prophets and that the LORD would put His Spirit upon them!”
Num 12:6 Then He said, “Hear now My words: If there is a prophet among you, I, the LORD, make Myself known to him in a vision; I speak to him in a dream.
The book of Numbers never contains the word ‘seer’ but rather, it contains ‘prophet’.
1Sam 9:9 (Formerly in Israel, when a man went to inquire of God, he spoke thus: “Come, let us go to the seer”; for he who is now called a prophet was formerly called a seer.)
1Chr 29:29 Now the acts of King David, first and last, indeed they are written in the book of Samuel the seer, in the book of Nathan the prophet, and in the book of Gad the seer
Samuel and Gad were referred as seer but Nathan was referred as prophet.
2Sam 24:11 Now when David arose in the morning, the word of the LORD came to the prophet Gad, David’s seer, saying
The book of 2nd Samuel goes to and fro between seer and prophet for Gad as in 2 Sam 24:11 where both are in the same verse. Nathan was never mentioned as a seer but always as a prophet. Hence, the term prophet came into usage sometime before the reign of king David (1065 BC). Since Nathan who was referred as a prophet confronts David for his sin of adultery and murder, he must be at least 30 years. Hence, the term prophet might have been in usage for a few decades before 1065 BC, which could be around 1095 BC.
The book of Numbers is a long and complex history of children of Israel which includes two census, but its final form is considered to be a Priestly redaction of a Yahwist source. As the book itself says, the it’s original sources may have been written as old as 1428 BC of Moses spoke in the plains of Moab by the Jordan. However revisions to the book of Numbers can be clearly around 1095 BC due to terms like ‘prophets’ not used by children of Israel prior to Samuel.