This is the second month of the Hebrew calendar. This is during the warm season when people are harvesting crops. It is during the last part of April and the first part of May on Western calendars.
"the rest of the members of their tribe—the priests and the Levites—and". The word "brothers" is used here because Zerubbabel, Jeshua, and the priests and Levites were all from the tribe of Levi; not all sons of the same man and woman.