1. Exposition

How does the dating here harmonize with that of 7:9?

Ezra 8:31 (ESV)

31 Then we departed from the river Ahava on the twelfth day of the first month, to go to Jerusalem. The hand of our God was on us, and he delivered us from the hand of the enemy and from ambushes by the way.

It appears as if the people only gather together on the first day of the twelfth month. After this initial gathering, there were three days of camping (Ezra 8:15) followed by eight days of waiting for the arrival of the Levites.