The assumed knowledge is that the Jews mourned during a part of the seventh month of the Hebrew calendar because in this month the remaining Jews in Jerusalem fled to Egypt after the murder of Gedaliah, whom the king of Babylon appointed as governor over Judah. The seventh month is during the last part of September and the first part of October on Western calendars. (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/translate-hebrewmonths]])
# for these seventy years
The assumed knowledge is that the people of Israel had been slaves in Babylon for 70 years. (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/translate-numbers]])
This question is asked to make the people think about what their real reason for fasting had been. It can be translated as a statement. Alternate translation: "you were not really fasting for me." (See: [[rc://en/ta/man/translate/figs-rquestion]])