The events of Chapters 1-10 are told chronologically.
All in Second Month
Though Chapters 7 and 9 refer to events of the first month their main focus is events of the second month. As such, Bemidbar 1-10 all takes place in one month, in the order written.
Chapters 1-4 – According to Abarbanel, the censuses and appointment of the Levites in place of firstborns, described in Bemidbar 1-4, all occurred in the second month as a simple reading of the verses would imply.
"וַיְהִי בְּיוֹם כַּלּוֹת מֹשֶׁה לְהָקִים אֶת הַמִּשְׁכָּן וַיִּמְשַׁח אֹתוֹ" – Abarbanel asserts that Moshe began anointing the vessels after erecting the Mishkan in the first month, but this was an extended process that lasted the entire month.
Dedication of the Altar – As the princes brought their sacrifices only after the vessels were anointed, the dedication of the altar took place in the second month. As such, with the exception of the first verse, all the events of Chapter 7 really occurred in the second month, after the census of chapters 1-4.
"הֵם הָעֹמְדִים עַל הַפְּקֻדִים" – Abarbanel points to the description of the princes as "those who officiated in the counting" to support his position. The verse can describe the princes in this manner because the census took place before the dedication of the altar.
"וַיַּקְרִיבוּ הַנְּשִׂאִים... בְּיוֹם הִמָּשַׁח אֹתוֹ" – This verse is difficult for this position as it suggests that the anointment took only one day and that the princes brought their sacrifices on that very day. Abarbanel asserts that the word "day" does not have to refer to a specific day but can speak of an extended period of time as well.1
Pesach Sheni – Abarbanel asserts that Chapter 9 only opens with Pesach in the first month as a prelude to the main topic of the chapter which is Pesach Sheni.2
Focus of Sefer Bemidbar
Census in First Year
Though the censuses of Chapters 1-4 are dated to the second month, they were really part of an extended process which began when the Tabernacle was being constructed. As such, the book of Bemidbar really opens with events of the first year, and then continues in order.
The events of Bemidbar 1-10 are not written in the order in which they occurred.
Later Events Told Earlier
The main story-line of Sefer Bemidbar begins in Chapter 9, in the first month of the second year. The earlier contain material dated later since they are thematically related to the Mishkan and simply form an appendix to the Books of Shemot and Vayikra.
